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Penn State University
1.
Dulny, Joseph Stephen.
Kinetic Monte Carlo Simulation of Vacancy and Adatom Diffusion in Ag(111) with a monolayer C60 adsorbate.
Degree: 2014, Penn State University
URL: https://submit-etda.libraries.psu.edu/catalog/22441 
► Recently, clean Ag(111) surfaces with monolayer C60 adsorbates have been studied with scanning tunneling microscopy and low energy electron diffraction. These studies revealed that the…
(more)
▼ Recently, clean Ag(111) surfaces with monolayer C60 adsorbates have been studied with scanning tunneling microscopy and low energy electron diffraction. These studies revealed that the C60 molecules form a commensurate (2*sqrt(3) x 2*sqrt(3))R30° phase on the Ag(111) substrate and when observed with STM, the C60 molecules appear either “bright” or “dim.” LEED studies showed that these two species of C60 are a result of the C60 taking two different orientations on the Ag substrate, one of which only occurs when the C60 is located over an Ag lattice vacancy. STM also shows the bright and dim C60 molecules change location over time. This dynamic “flipping” behavior implies that vacancy diffusion in the Ag lattice is taking place. Here, using the kinetic Monte Carlo algorithm, I model the diffusion of vacancies in the Ag lattice. Additionally, more complex simulations involving creation/destruction of vacancies/adatoms, spatial C60 flip correlation, adatom diffusion, adatom interactions with vacancies, and “superbright” C60 molecules are also presented and studied. Datasets collected from these simulations are compared to experimental data on the flipping rate of the C60 molecules vs. temperature, the bright/dim C60 ratio vs. temperature, and the “superbright” flipping rate of the C60 molecules vs. temperature. Additionally, the system of C60 on Au(111) is studied using the models developed in this dissertation. For vacancy diffusion, it is concluded that the number of vacancies in the lattice is not fixed as the temperature of the lattice changes. The source/sink of vacancies is shown to most likely be the domain boundaries of the system, as models allowing this type of diffusion approximate the experimental results and show spatially correlated flipping. A strong equilibrium number of vacancies forms in the lattice when vacancy diffusion through domain boundaries is allowed. Bulk vacancy diffusion is shown to be highly unlikely. Spatial flipping correlation is studied closely and it is concluded that it is directly related to vacancy number. Adatoms are also included in the simulation and allowed to diffuse in the hollow sites of the surface lattice. These serve to increase the flipping correlation and decrease the flipping rate. It is shown that adatoms forming a triangular pedestal beneath C60 is likely the cause of the superbright C60. Finally, this model is shown to also accurately simulate the system of C60 on Au(111).
Advisors/Committee Members: Renee Denise Diehl, Dissertation Advisor/Co-Advisor, Julian Decatur Maynard Jr., Committee Member, Jorge Osvaldo Sofo, Committee Member, Long Qing Chen, Committee Member.
Subjects/Keywords: Vacancies; Adatoms; Diffusion; Ag; Au; C60; Buckyball; Surface Physics; Kinetic Monte Carlo
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APA (6th Edition):
Dulny, J. S. (2014). Kinetic Monte Carlo Simulation of Vacancy and Adatom Diffusion in Ag(111) with a monolayer C60 adsorbate. (Thesis). Penn State University. Retrieved from https://submit-etda.libraries.psu.edu/catalog/22441
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Chicago Manual of Style (16th Edition):
Dulny, Joseph Stephen. “Kinetic Monte Carlo Simulation of Vacancy and Adatom Diffusion in Ag(111) with a monolayer C60 adsorbate.” 2014. Thesis, Penn State University. Accessed January 27, 2021.
https://submit-etda.libraries.psu.edu/catalog/22441.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
MLA Handbook (7th Edition):
Dulny, Joseph Stephen. “Kinetic Monte Carlo Simulation of Vacancy and Adatom Diffusion in Ag(111) with a monolayer C60 adsorbate.” 2014. Web. 27 Jan 2021.
Vancouver:
Dulny JS. Kinetic Monte Carlo Simulation of Vacancy and Adatom Diffusion in Ag(111) with a monolayer C60 adsorbate. [Internet] [Thesis]. Penn State University; 2014. [cited 2021 Jan 27].
Available from: https://submit-etda.libraries.psu.edu/catalog/22441.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Council of Science Editors:
Dulny JS. Kinetic Monte Carlo Simulation of Vacancy and Adatom Diffusion in Ag(111) with a monolayer C60 adsorbate. [Thesis]. Penn State University; 2014. Available from: https://submit-etda.libraries.psu.edu/catalog/22441
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Penn State University
2.
Fernandez, Laura Elizabeth.
Proton-coupled Electron Transfer Reactions: Electrochemical Method Development and Applications
.
Degree: 2013, Penn State University
URL: https://submit-etda.libraries.psu.edu/catalog/17415
► Proton-coupled electron transfer (PCET) reactions involve the transfer of single or multiple electrons and protons in sequential or concerted fashion. PCET reactions are important in…
(more)
▼ Proton-coupled electron transfer (PCET) reactions involve the transfer of single or multiple electrons and protons in sequential or concerted fashion. PCET reactions are important in biological systems such as photosynthesis and respirations, and in chemical systems, such as electrochemistry and catalysis. The applications studied here are relevant to systems such as artificial photosynthesis and water-splitting devices. Of central importance to PCET reactions is the donor-acceptor distance and effective frequency. The first application, which models proton relays that occur in fuel cells, artificial photosynthesis and enzyme reactions, illustrates the importance of the donor-acceptor distance in the case of a single and a double proton transfer. In the second application, we investigate electrocatalysts inspired by hydrogenase enzymes, which oxidize and produce H2 in nature. In this application, which is relevant to water-splitting devices, we looked into whether a sequential or concerted mechanism was more preferable for nickel-based catalysts with pendant amines. We then continued this investigation to find faster catalysts for H2 oxidation and H2 reduction using more flexible amines with nickel centers. From these studies of PCET reactions, we found that theoretical investigations can aid in the analysis of experimental results and provide predictions for future experiments and in some cases help to reanalyze experimental interpretation.
Advisors/Committee Members: Sharon Hammes Schiffer, Dissertation Advisor/Co-Advisor, Lasse Jensen, Committee Member, Squire J Booker, Committee Member, Jorge Osvaldo Sofo, Committee Member.
Subjects/Keywords: Proton-Coupled Electron Transfer; PCET; Electrochemistry; Theoretical
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APA (6th Edition):
Fernandez, L. E. (2013). Proton-coupled Electron Transfer Reactions: Electrochemical Method Development and Applications
. (Thesis). Penn State University. Retrieved from https://submit-etda.libraries.psu.edu/catalog/17415
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Chicago Manual of Style (16th Edition):
Fernandez, Laura Elizabeth. “Proton-coupled Electron Transfer Reactions: Electrochemical Method Development and Applications
.” 2013. Thesis, Penn State University. Accessed January 27, 2021.
https://submit-etda.libraries.psu.edu/catalog/17415.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
MLA Handbook (7th Edition):
Fernandez, Laura Elizabeth. “Proton-coupled Electron Transfer Reactions: Electrochemical Method Development and Applications
.” 2013. Web. 27 Jan 2021.
Vancouver:
Fernandez LE. Proton-coupled Electron Transfer Reactions: Electrochemical Method Development and Applications
. [Internet] [Thesis]. Penn State University; 2013. [cited 2021 Jan 27].
Available from: https://submit-etda.libraries.psu.edu/catalog/17415.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Council of Science Editors:
Fernandez LE. Proton-coupled Electron Transfer Reactions: Electrochemical Method Development and Applications
. [Thesis]. Penn State University; 2013. Available from: https://submit-etda.libraries.psu.edu/catalog/17415
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Penn State University
3.
Gunaratne, K. Don Dasitha.
Photoelectron Imaging Spectroscopic Investigations of Transition Metal Silicides and Oxides.
Degree: 2012, Penn State University
URL: https://submit-etda.libraries.psu.edu/catalog/13133
► This dissertation presents the experimental progress in the use of photoelectron imaging spectroscopy to probe the electronic structure of negatively charged transition metal silicides and…
(more)
▼ This dissertation presents the experimental progress in the use of photoelectron imaging spectroscopy to probe the electronic structure of negatively charged transition metal silicides and oxides. By measuring the electronic transitions that occur due to the use of an appropriate photon energy, the electron affinity of the neutral species can be measured and the ground and excited electronic states of the anion and neutral can be deduced. The introductory chapter explains the basics of photoelectron spectroscopy and how it is coupled with recently developed imaging techniques to simultaneously obtain energy and angular distribution of the photodetached electrons. The β parameter, which is instrumental in quantifying the angular distribution, is discussed in detail. The motivation for pursuing the transition metal silicide and oxide studies and their increasing importance in technology is also emphasized.
Photoelectron imaging spectroscopy employed in our laboratory involves custom-built ultra high-vacuum instrumentation which couples a time-of-flight (TOF) mass spectrometer with an electron imaging apparatus. Chapter 2 discloses the details of the experimental setup required to conduct these studies; from the laser ablation techniques that form the species of interest, to the mass selection of the negatively charged clusters and the subsequent photodetachment of electrons from the highest occupied molecular orbitals of the anion. The modifications made to the safety features of the instrument, in addition to the improvements to the high-vacuum configuration, are described in detail.
The first known photoelectron spectroscopic investigation of the ZrSi- diatomic species has been conducted as part of this dissertation. Chapter 3 discusses the results of the 532 nm and 355 nm wavelength experiments on ZrSi-. Conflicts between the two previous theoretical studies which proposed the ground
state of the neutral has been noted while new electronic
state assignments have been assigned based on experimental evidence. This study supports the 2Σ+: (1σ)2 (1π)4 (1δ)0 (2σ)2 (3σ)1 anion ground electronic
state (and valence orbital electron configuration) which is in agreement with theoretical results. The assigned ground
state of the neutral, however, differs from that based on current theoretical results. The ground
state of ZrSi was assigned as the 3Σ+: (1σ)2 (1π)4 (1δ)0 (2σ)1 (3σ)1 based on the angular distribution and the relative intensities of the photoelectron signal. A low-lying excited
state of the neutral was assigned as 3Πi with valence orbital configuration, (1σ)2 (1π)3 (1δ)0 (2σ)2 (3σ)1. The electron affinity of ZrSi is measured as 1.584 eV, while a low-lying excited
state of the neutral is identified 0.238 eV above the ZrSi neutral ground
state. Additionally, Franck-Condon simulations were performed to compare with the experimental photoelectron spectrum and estimate the vibrational temperature of the anions created in our cluster source.
Extending the transition metal silicide studies to other metals, Chapter 4…
Advisors/Committee Members: Albert Welford Castleman Jr., Dissertation Advisor/Co-Advisor, Thomas E Mallouk, Committee Member, Mark Maroncelli, Committee Member, Jorge Osvaldo Sofo, Committee Member.
Subjects/Keywords: Photoelectron spectroscopy; Electron Imaging; Photoelectron Angular Distribution; Transition metal; Silicon; Zinc Oxide
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APA (6th Edition):
Gunaratne, K. D. D. (2012). Photoelectron Imaging Spectroscopic Investigations of Transition Metal Silicides and Oxides. (Thesis). Penn State University. Retrieved from https://submit-etda.libraries.psu.edu/catalog/13133
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Chicago Manual of Style (16th Edition):
Gunaratne, K Don Dasitha. “Photoelectron Imaging Spectroscopic Investigations of Transition Metal Silicides and Oxides.” 2012. Thesis, Penn State University. Accessed January 27, 2021.
https://submit-etda.libraries.psu.edu/catalog/13133.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
MLA Handbook (7th Edition):
Gunaratne, K Don Dasitha. “Photoelectron Imaging Spectroscopic Investigations of Transition Metal Silicides and Oxides.” 2012. Web. 27 Jan 2021.
Vancouver:
Gunaratne KDD. Photoelectron Imaging Spectroscopic Investigations of Transition Metal Silicides and Oxides. [Internet] [Thesis]. Penn State University; 2012. [cited 2021 Jan 27].
Available from: https://submit-etda.libraries.psu.edu/catalog/13133.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Council of Science Editors:
Gunaratne KDD. Photoelectron Imaging Spectroscopic Investigations of Transition Metal Silicides and Oxides. [Thesis]. Penn State University; 2012. Available from: https://submit-etda.libraries.psu.edu/catalog/13133
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Penn State University
4.
Tang, Youjian.
Two Dimensional Layered materials: First-principle Investigation.
Degree: 2016, Penn State University
URL: https://submit-etda.libraries.psu.edu/catalog/28914
► Two-dimensional layered materials have emerged as a fascinating research area due to their unique physical and chemical properties, which differ from those of their bulk…
(more)
▼ Two-dimensional layered materials have emerged as a fascinating research area
due to their unique physical and chemical properties, which differ from those of
their bulk counterparts. Some of these unique properties are due to carriers and
transport being confined to 2 dimensions, some are due to lattice symmetry, and
some arise from their large surface area, gateability, stackability, high mobility,
spin transport, or optical accessibility. How to modify the electronic and magnetic
properties of two-dimensional layered materials for desirable long-term applications
or fundamental physics is the main focus of this thesis. We explored the methods
of adsorption, intercalation, and doping as ways to modify two-dimensional layered
materials, using density functional theory as the main computational methodology.
Chapter 1 gives a brief review of density functional theory. Due to the difficulty
of solving the many-particle Schrödinger equation, density functional theory was
developed to find the ground-
state properties of many-electron systems through
an examination of their charge density, rather than their wavefunction. This
method has great application throughout the chemical and material sciences, such
as modeling nano-scale systems, analyzing electronic, mechanical, thermal, optical
and magnetic properties, and predicting reaction mechanisms.
Graphene and transition metal dichalcogenides are arguably the two most
important two-dimensional layered materials in terms of the scope and interest
of their physical properties. Thus they are the main focus of this thesis. In
chapter 2, the structure and electronic properties of graphene and transition
metal dichalcogenides are described. Alkali adsorption onto the surface of bulk
graphite and metal intecalation into transition metal dichalcogenides – two methods
of modifying properties through the introduction of metallic atoms into layered
systems – are described in chapter 2.
Chapter 3 presents a new method of tuning the electronic properties of 2D
materials: resonant physisorption. An example is given for adsorption of polycyclic
aromatic hydrocarbon molecules onto graphene. The energy levels of these molecules
were fine tuned to make them resonate with the graphene Fermi level, thus enhancing
iiithe strength of their effect on the graphene electronic structure.
Chapter 4 develops the idea of coupling two distinct surface adsorption systems
across a suspended atomically thin membrane. We examine a system of dual-sided
adsorption of potassium onto a graphene membrane. The sequence of adsorption
patterns predicted undergoes a striking devil’s staircase of intermediate coverage
fractions as the difference in adsorbate chemical potential betweeen the two sides
of the membrane varies.
Chapter 5 is devoted to magnetic and band structure engineering of transition
metal dichalcogenides through introduction of magnetic atoms into the lattice.
Semiconducting transition metal dichalcogenide systems such as MoS2 and WS2
have band gaps suitable for electronic and optoelectronic applications,…
Advisors/Committee Members: Vincent Henry Crespi, Dissertation Advisor/Co-Advisor, Jun Zhu, Committee Member, Jorge Osvaldo Sofo, Committee Member, Zi Kui Liu, Committee Member.
Subjects/Keywords: Two Dimensional; graphene; First-Principle; transition metal dichalcogenides
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APA ·
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Manager
APA (6th Edition):
Tang, Y. (2016). Two Dimensional Layered materials: First-principle Investigation. (Thesis). Penn State University. Retrieved from https://submit-etda.libraries.psu.edu/catalog/28914
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Chicago Manual of Style (16th Edition):
Tang, Youjian. “Two Dimensional Layered materials: First-principle Investigation.” 2016. Thesis, Penn State University. Accessed January 27, 2021.
https://submit-etda.libraries.psu.edu/catalog/28914.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
MLA Handbook (7th Edition):
Tang, Youjian. “Two Dimensional Layered materials: First-principle Investigation.” 2016. Web. 27 Jan 2021.
Vancouver:
Tang Y. Two Dimensional Layered materials: First-principle Investigation. [Internet] [Thesis]. Penn State University; 2016. [cited 2021 Jan 27].
Available from: https://submit-etda.libraries.psu.edu/catalog/28914.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Council of Science Editors:
Tang Y. Two Dimensional Layered materials: First-principle Investigation. [Thesis]. Penn State University; 2016. Available from: https://submit-etda.libraries.psu.edu/catalog/28914
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Penn State University
5.
Xu, Enshi.
COMPUTATIONAL STUDY OF CARBON NANOMATERIALS: NANOTHREADS AND NANOPOROUS CARBON.
Degree: 2016, Penn State University
URL: https://submit-etda.libraries.psu.edu/catalog/vx021f082
► Place abstract below. Carbon nano-materials can be categorized by their hybridization and dimension: whether they are sp2 or sp3 hybridized, and whether they are zero,…
(more)
▼ Place abstract below.
Carbon nano-materials can be categorized by their hybridization and dimension: whether they are sp
2 or sp
3 hybridized, and whether they are zero, one, two or three dimensional material. A recent experiment breakthrough, cold compression of solid benzene into ordered product that is stable back to ambient condition, brought to the front stage a new sp
3 hybridized material which is also one dimensional, and this material, belonging in the category of one dimensional sp
3 carbon, has certain advantages over the previously considered polymers or nanowires: polymers have too much structural flexibility, nanowires are too wide that most of the atoms are still in the diamond bulk
state. We name the material ``carbon nanothread''.
Following a concise introduction in Chapter 1 of the structures and basic properties of carbon material classified by their hybridization and dimensionality and a practical introduction in Chapter 2 to the simulation methods used in studying carbon nanothreads, the author presents a systematic enumeration scheme to generate all the structure candidates for carbon nanothreads in Chapter 3, a work that has been published in early 2015. The visualization of the lowest energy structures and a brief discussion of their properties follow the enumeration scheme. In the later sections of Chapter 3, the author shows possible chemical reactions leading to these carbon nanothreads starting from benzene, along with the structures of intermediates, a work done not by the author himself but by the author's collaborators and a work that is an important and integral part to understand the whole picture of nanothreads. Some on-going and proposed directions to utilize the physical properties of carbon nanothreads for applications are proposed in Chapter 3 as well.
With the structure candidates at hand, we are equipped to analyze the sample synthesized in experiments, by comparing the calculated observables of the candidate structures to the experiments, a topic of Chapter 4. Raman spectrum analysis is the most extensively studied one, and other experiments are also briefly mentioned. This part of the work is an on-going, unpublished effort.
Tuning the reactions pathways by using different precursors will be interesting, and boron nitride nanothreads naturally comes into consideration by the analog of boron nitride nanotube. Chapter 5 focuses on the structures of boron nitride versions of nanothreads, starting from a proposed molecular precursor and covering all the possible intermediates and mapping out potential reaction pathways. Due to the partial ionic nature of boron nitride compound and symmetry breaking, some aspects of the polarization of BN nanothread, having a density as large as the common ferroelectric material BaTiO
3,
are discussed, envisioning possible applications.
In Chapter 6, the author's work prior to the nanothread efforts is presented. The work focuses on another category of carbon material: sp
2 hybridized carbon with true three-dimensional…
Advisors/Committee Members: Vincent Henry Crespi, Dissertation Advisor/Co-Advisor, Mauricio Terrones Maldonado, Committee Member, Jorge Osvaldo Sofo, Committee Member, John V. Badding, Outside Member.
Subjects/Keywords: Nanothread; Density Functional Theory; Carbon Nano-materials; Schwarzites; Raman Spectroscopy
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APA ·
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APA (6th Edition):
Xu, E. (2016). COMPUTATIONAL STUDY OF CARBON NANOMATERIALS: NANOTHREADS AND NANOPOROUS CARBON. (Thesis). Penn State University. Retrieved from https://submit-etda.libraries.psu.edu/catalog/vx021f082
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Chicago Manual of Style (16th Edition):
Xu, Enshi. “COMPUTATIONAL STUDY OF CARBON NANOMATERIALS: NANOTHREADS AND NANOPOROUS CARBON.” 2016. Thesis, Penn State University. Accessed January 27, 2021.
https://submit-etda.libraries.psu.edu/catalog/vx021f082.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
MLA Handbook (7th Edition):
Xu, Enshi. “COMPUTATIONAL STUDY OF CARBON NANOMATERIALS: NANOTHREADS AND NANOPOROUS CARBON.” 2016. Web. 27 Jan 2021.
Vancouver:
Xu E. COMPUTATIONAL STUDY OF CARBON NANOMATERIALS: NANOTHREADS AND NANOPOROUS CARBON. [Internet] [Thesis]. Penn State University; 2016. [cited 2021 Jan 27].
Available from: https://submit-etda.libraries.psu.edu/catalog/vx021f082.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Council of Science Editors:
Xu E. COMPUTATIONAL STUDY OF CARBON NANOMATERIALS: NANOTHREADS AND NANOPOROUS CARBON. [Thesis]. Penn State University; 2016. Available from: https://submit-etda.libraries.psu.edu/catalog/vx021f082
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Penn State University
6.
Chia, Cheng Ing.
Geometrically constrained nanoscale materials.
Degree: 2012, Penn State University
URL: https://submit-etda.libraries.psu.edu/catalog/14962
► Nano-materials are a main topic in condensed matter research because of unusual properties that originate from quantum mechanical effects at this length scale. In this…
(more)
▼ Nano-materials are a main topic in condensed matter research because of unusual properties that originate from quantum mechanical effects at this length scale. In this thesis I consider nano-materials from a geometrical perspective. The atoms/molecules could be restricted topologically; their electronic interactions (reaction through charge transfer), however, are still allowed. The physical and chemical properties of materials under this restriction change dramatically. This dissertation is mainly devoted to the study of those changes in physical and chemical properties, based on first-principles computation techniques (Density Functional Theory).
DFT is an ab-initio quantum mechanical computation method used for materials as well as molecules. It predicts stable molecular/crystal structures and describes a chemical reaction and phase transition. It also provides an understanding and quantitative prediction of materials properties, including mechanical, thermal, electrical, optical, magnetic, and chemical properties. In this thesis I mainly use DFT to examine the energetics and band structures of geometrically constrained nano-materials. A brief overview of Density Functional Theory is given in Ch.1.
Graphene (a single layer membrane of carbon atoms) and hexagonal boron nitride, which as a similar structure to that of graphene are basic building blocks for all the work in this thesis. Ch.2 covers some basic structural and electronic properties of these materials. In Ch. 3, I extend that to graphene nanoribbons, finite-width stripes of graphene.
In Ch.4, I propose a topological frustrated system based on a graphene membrane. A suspended and impenetrable graphene layer breaks the translational symmetry in vacuum and divides it into two distinct sub-spaces. Imagine alkali atoms released above the layer and halogen from below. The layer prevents direct interaction between alkali and halogen as each species is restricted in its own half-space, so the formation of a regular salt crystal is forbidden. However, they could still interact via charge transfer through the sheet. The charge transfer from alkali breaks halogen molecular bonds and creates a cross-layer alkali/halogen dipole pair. This uncompensated collective dipolar interaction penalizes the halogen states and raises them to the Fermi level. It thus generates an unusual band-structure with nearly flat bands at Fermi level. A slight change in the halogen position causes the dramatic change in electronic structures (a semiconductor-semimetal-metal transition), leading to the breakdown of Born-Oppenheimer approximation and possibly to strong many-body effects (polaron, superconductivity...). The stable open-shell halogen also suggests a potential catalytic behavior by accommodating to a reactant transition
state. This system defines a new regime of chemical interaction that is governed by a topological constraint. Viewed as surface physics, the properties of a given side can be tuned by changing the species on the opposite side.
In Ch.5, I replace the…
Advisors/Committee Members: Vincent Henry Crespi, Dissertation Advisor/Co-Advisor, Jorge Osvaldo Sofo, Committee Member, Jun Zhu, Committee Member, Thomas E Mallouk, Committee Member.
Subjects/Keywords: DFT; graphene; topological frustration; nanoribbon
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APA ·
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MLA ·
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Manager
APA (6th Edition):
Chia, C. I. (2012). Geometrically constrained nanoscale materials. (Thesis). Penn State University. Retrieved from https://submit-etda.libraries.psu.edu/catalog/14962
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Chicago Manual of Style (16th Edition):
Chia, Cheng Ing. “Geometrically constrained nanoscale materials.” 2012. Thesis, Penn State University. Accessed January 27, 2021.
https://submit-etda.libraries.psu.edu/catalog/14962.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
MLA Handbook (7th Edition):
Chia, Cheng Ing. “Geometrically constrained nanoscale materials.” 2012. Web. 27 Jan 2021.
Vancouver:
Chia CI. Geometrically constrained nanoscale materials. [Internet] [Thesis]. Penn State University; 2012. [cited 2021 Jan 27].
Available from: https://submit-etda.libraries.psu.edu/catalog/14962.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Council of Science Editors:
Chia CI. Geometrically constrained nanoscale materials. [Thesis]. Penn State University; 2012. Available from: https://submit-etda.libraries.psu.edu/catalog/14962
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Penn State University
7.
Puls, Conor P.
Electronic Band Structure Effects in Monolayer, Bilayer, and Hybrid Graphene Structures.
Degree: 2012, Penn State University
URL: https://submit-etda.libraries.psu.edu/catalog/15255
► Since its discovery in 2005, graphene has been the focus of intense theoretical and experimental study owing to its unique two-dimensional band structure and related…
(more)
▼ Since its discovery in 2005, graphene has been the focus of intense theoretical and experimental study owing to its unique two-dimensional band structure and related electronic properties. In this thesis, we explore the electronic properties of graphene structures from several perspectives including the magnetoelectrical transport properties of monolayer graphene, gap engineering and measurements in bilayer graphene, and anomalous quantum oscillation in the monolayer-bilayer graphene hybrids. We also explored the device implications of our findings, and the application of some experimental techniques developed for the graphene work to the study of a complex oxide, Ca3Ru2O7, exhibiting properties of strongly correlated electrons.
Graphene's high mobility and ballistic transport over device length scales, make it suitable for numerous applications. However, two big challenges remain in the way: maintaining high mobility in fabricated devices, and engineering a band gap to make graphene compatible with logical electronics and various optical devices. We address the first challenge by experimentally evaluating mobilities in scalable monolayer graphene-based field effect transistors (FETs) and dielectric-covered Hall bars. We find that the mobility is limited in these devices, and is roughly inversely proportional to doping. By considering interaction of graphene's Dirac fermions with with local charged impurities at the interface between graphene and the top-gate dielectric, we find that Coulomb scattering is responsible for degraded mobility.
Even in the cleanest devices, a band gap is still desirable for electronic applications of graphene. We address this challenge by probing the band structure of bilayer graphene, in which a field-tunable energy band gap has been theoretically proposed. We use planar tunneling spectroscopy of exfoliated bilayer graphene flakes demonstrate both measurement and control of the energy band gap. We find that both the Fermi level and electronic structure are highly sensitive to tunnel bias-induced charging in these devices, an effect that is traditionally neglected in other materials. However, careful consideration of both these effects and non-ideal tunneling processes allows extraction of valuable information from the tunneling spectra. We compare the tunable insulating
state to our transport studies of bilayer graphene-based FETs with similar dielectric environments. This work, as well as our work on top-gated monolayer-based devices, identifies the integration of graphene and a gate dielectric as being the next great challenge towards the realization of graphene-based electronics.
We also report the discovery of anomalous quantum oscillations in magnetotransport measurements of monolayer and bilayer graphene hybrids. In these graphene hybrid structures, the Fermi levels of either portion lock at their interface, and the greatly different energy scales of emergent Landau levels support strong charge imbalance. The nature the interface states are yet to be clarified.
…
Advisors/Committee Members: Dr Ying Liu, Dissertation Advisor/Co-Advisor, Jorge Osvaldo Sofo, Committee Member, Qi Li, Committee Member, Thomas E Mallouk, Committee Member.
Subjects/Keywords: graphene; bilayer; hybrid; band gap engineering; impurity scattering; Ca3Ru2O7
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APA (6th Edition):
Puls, C. P. (2012). Electronic Band Structure Effects in Monolayer, Bilayer, and Hybrid Graphene Structures. (Thesis). Penn State University. Retrieved from https://submit-etda.libraries.psu.edu/catalog/15255
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Chicago Manual of Style (16th Edition):
Puls, Conor P. “Electronic Band Structure Effects in Monolayer, Bilayer, and Hybrid Graphene Structures.” 2012. Thesis, Penn State University. Accessed January 27, 2021.
https://submit-etda.libraries.psu.edu/catalog/15255.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
MLA Handbook (7th Edition):
Puls, Conor P. “Electronic Band Structure Effects in Monolayer, Bilayer, and Hybrid Graphene Structures.” 2012. Web. 27 Jan 2021.
Vancouver:
Puls CP. Electronic Band Structure Effects in Monolayer, Bilayer, and Hybrid Graphene Structures. [Internet] [Thesis]. Penn State University; 2012. [cited 2021 Jan 27].
Available from: https://submit-etda.libraries.psu.edu/catalog/15255.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Council of Science Editors:
Puls CP. Electronic Band Structure Effects in Monolayer, Bilayer, and Hybrid Graphene Structures. [Thesis]. Penn State University; 2012. Available from: https://submit-etda.libraries.psu.edu/catalog/15255
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Penn State University
8.
Wang, Yuanxi.
Theory of two-dimensional materials: synthesis, properties, and structural engineering.
Degree: 2016, Penn State University
URL: https://submit-etda.libraries.psu.edu/catalog/3b591857h
► In this dissertation, I study the synthesis (and post-synthesis modifications), properties, and structural engineering of two-dimensional materials, using atomistic modeling techniques such as empirical forcefields…
(more)
▼ In this dissertation, I study the synthesis (and post-synthesis modifications), properties, and structural engineering of two-dimensional materials, using atomistic modeling techniques such as empirical forcefields and density functional theory. The dissertation is divided into four parts. The first part consists of four chapters: in Chapters 1-3 I give an overview on density functional theory and how vibrational properties and optical properties can be calculated within the DFT framework; in Chapter 4 a brief review on two-dimensional materials is given.
The second part is devoted to the synthesis and post-synthesis modifications of two-dimensional materials. In Chapter 5 I investigate the intercalation of hexagonal boron nitride and graphite using Bronsted acids such as H3PO4. DFT calculations show that dipolar interactions between acids molecules and the 2D sheets drive the intercalation process.
In Chapter 6 I study stripe patterns of W and Mo atoms in triangular monolayers of WxMo1-xS2 alloys. DFT calculations suggest that stripe ordering is kinetically driven, governed by fluctuations in local thermodynamic conditions during growth. In addition, I show that the striped phase alloy is electronically isotropic but vibrationally anisotropic, due to the nearly-identical electronic properties but very different atomic masses of Mo and W.
The third part is devoted to computation of vibrational and optical properties of molybdenum and tungsten disulfides. In Chapter 7 we investigate the optical signatures of defect-bound excitons in monolayer WS2. I show that the optical transitions between the highest valence band and mid-gap states introduced by sulfur vacancy defects have finite transition matrix elements. These results agrees with the measured photoluminescence spectra of monolayer WS2 grown by chemical vapor deposition, where spatially resolved photoluminescence at low temperatures revealed two bound excitons. To explain the anomaly in the thermal activation energy of the bound exciton, we propose that excitons are bound to negatively charged defects where two channels of radiative recombinations are allowed.
Chapter 8 focuses on intervalley scattering processes in monolayer MoS2, as probed by resonance raman spectroscopy, where the incident laser energy is varied across the A and B excitonic levels. We focus on two Raman peaks that are dispersive, a clear signature of second-order processes involving intervalley scattering. Using group theory and DFT calculations, selection rules are established for intervalley scattering processes
mediated by acoustic phonons.
In Chapter 9 I investigate Second Harmonic Generation (SHG) in monolayer WS2. Its second order nonlinear susceptibility is nearly three orders of magnitude larger than other common nonlinear crystals. Density functional theory calculations suggest that the origin of the large nonlinear susceptibility lies in resonance enhancement and sharp features in the joint density of states.
In the final part, I explore possible methods of manipulating the…
Advisors/Committee Members: Vincent Henry Crespi, Dissertation Advisor/Co-Advisor, Vincent Henry Crespi, Committee Chair/Co-Chair, Jorge Osvaldo Sofo, Committee Member, Mauricio Terrones Maldonado, Committee Member, Thomas E Mallouk, Outside Member.
Subjects/Keywords: two-dimensional materials; density functional theory
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APA ·
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MLA ·
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APA (6th Edition):
Wang, Y. (2016). Theory of two-dimensional materials: synthesis, properties, and structural engineering. (Thesis). Penn State University. Retrieved from https://submit-etda.libraries.psu.edu/catalog/3b591857h
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Chicago Manual of Style (16th Edition):
Wang, Yuanxi. “Theory of two-dimensional materials: synthesis, properties, and structural engineering.” 2016. Thesis, Penn State University. Accessed January 27, 2021.
https://submit-etda.libraries.psu.edu/catalog/3b591857h.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
MLA Handbook (7th Edition):
Wang, Yuanxi. “Theory of two-dimensional materials: synthesis, properties, and structural engineering.” 2016. Web. 27 Jan 2021.
Vancouver:
Wang Y. Theory of two-dimensional materials: synthesis, properties, and structural engineering. [Internet] [Thesis]. Penn State University; 2016. [cited 2021 Jan 27].
Available from: https://submit-etda.libraries.psu.edu/catalog/3b591857h.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Council of Science Editors:
Wang Y. Theory of two-dimensional materials: synthesis, properties, and structural engineering. [Thesis]. Penn State University; 2016. Available from: https://submit-etda.libraries.psu.edu/catalog/3b591857h
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Penn State University
9.
Mubin, Shafat A.
Theory of Thermodynamics and Kinetics of Benzene Adsorption on Ag(111).
Degree: 2016, Penn State University
URL: https://submit-etda.libraries.psu.edu/catalog/13319svm5300
► The adsorbed layer of benzene on Ag(111) is studied using molecular dynamics techniques. A force-field is developed to describe benzene-Ag interaction, involving the introduction of…
(more)
▼ The adsorbed layer of benzene on Ag(111) is studied using molecular dynamics techniques. A force-field is developed to describe benzene-Ag interaction, involving the introduction of a fictitious site at the center of benzene, and the binding energy E
b=0.64 eV and the vanishing coverage prefactor of desorption k
0 = (5.0±3.0) × 10
14 s
-1 are obtained from the force-field. Subsequently, the intermolecular interaction is studied and found to be dominated by substrate-mediated interactions, primarily the pairwise interaction between adsorbates produced by scattering of Shockley states. The z-dependence of these substrate-mediated interactions is derived and found to create noticeable difference to the order-disorder transition temperature of the adsorbed benzene monolayer. These substrate-mediated interactions are further validated by simulating high-coverage temperature-programmed desorption (TPD) spectra. In simulating high-coverage TPD, the bond-boost method is used to boost the simulated timescale several orders of magnitude. In the process, the impact of surface defects on TPD spectra is also investigated, and found to slightly shift the peak desorption temperatures and considerably broaden the trailing edge of the spectra.
Advisors/Committee Members: Kristen Ann Fichthorn, Dissertation Advisor/Co-Advisor, Kristen Ann Fichthorn, Committee Chair/Co-Chair, Milton Walter Cole, Committee Member, Jorge Osvaldo Sofo, Committee Member, Adrianus C Van Duin, Outside Member.
Subjects/Keywords: Benzene; Monolayer; Desorption; Accelerated MD; Bond-boost Method; Force-field; Order-disorder; Ag(111); TPD; Substrate-mediated Interaction; Molecular Dynamics; Surface Defects
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APA ·
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APA (6th Edition):
Mubin, S. A. (2016). Theory of Thermodynamics and Kinetics of Benzene Adsorption on Ag(111). (Thesis). Penn State University. Retrieved from https://submit-etda.libraries.psu.edu/catalog/13319svm5300
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Chicago Manual of Style (16th Edition):
Mubin, Shafat A. “Theory of Thermodynamics and Kinetics of Benzene Adsorption on Ag(111).” 2016. Thesis, Penn State University. Accessed January 27, 2021.
https://submit-etda.libraries.psu.edu/catalog/13319svm5300.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
MLA Handbook (7th Edition):
Mubin, Shafat A. “Theory of Thermodynamics and Kinetics of Benzene Adsorption on Ag(111).” 2016. Web. 27 Jan 2021.
Vancouver:
Mubin SA. Theory of Thermodynamics and Kinetics of Benzene Adsorption on Ag(111). [Internet] [Thesis]. Penn State University; 2016. [cited 2021 Jan 27].
Available from: https://submit-etda.libraries.psu.edu/catalog/13319svm5300.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Council of Science Editors:
Mubin SA. Theory of Thermodynamics and Kinetics of Benzene Adsorption on Ag(111). [Thesis]. Penn State University; 2016. Available from: https://submit-etda.libraries.psu.edu/catalog/13319svm5300
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Penn State University
10.
Raju, Muralikrishna.
Applications of Molecular Dynamics, Monte Carlo and Metadynamics Simulations using ReaxFF Reactive Force Fields to Fluid/Solid Interfaces.
Degree: 2015, Penn State University
URL: https://submit-etda.libraries.psu.edu/catalog/23853
► The interaction of dense fluids (water, polar organic solvents, room temperature ionic liquids, etc.) with solid substrates controls many chemical processes encountered in nature and…
(more)
▼ The interaction of dense fluids (water, polar organic solvents, room temperature ionic liquids, etc.) with solid substrates controls many chemical processes encountered in nature and industry. The key features of fluid-solid interfaces (FSIs) are the high mobility and often reactivity of the fluid phase, and the structural control provided by the solid phase. In this dissertation we apply molecular modeling methods to study FSIs in the following systems:
1. Dissociation of water on titania surfaces
We studied the adsorption and dissociation of water at 300 K on the following TiO2 surfaces: anatase (101), (100), (112), (001) and rutile (110) at various water coverages, using a recently developed ReaxFF reactive force field. The molecular and dissociative adsorption configurations predicted by ReaxFF for various water coverages agree with previous theoretical studies and experiment. ReaxFF predicts a complex distribution of water on these surfaces depending on an intricate balance between the spacing of the adsorption sites (under-coordinated Ti and O surface atoms), water-surface interactions, and water-water interactions. Using molecular dynamics simulations to quantify water dissociation over the TiO2 surfaces at various water coverages, we find that the extent of water dissociation predicted by the ReaxFF reactive force field is in general agreement with previous density-functional theory studies and experiments. We demonstrate a correlation between the extent of water dissociation on different TiO2 surfaces and the strength of hydrogen bonding between adsorbed water molecules and water outside the adsorbed layer, as evidenced by the red shift of the O-H vibrational stretching mode of adsorbed water.
2. Mechanisms of Oriented Attachment in TiO2 nanocrystals
Oriented attachment (OA) of nanocrystals is now widely recognized as a key process in the solution-phase growth of hierarchical nanostructures. However, the microscopic origins of OA remain unclear. Using the same ReaxFF Ti/O/H reactive force field employed in the previous study, we perform molecular dynamics simulations to study the aggregation of various titanium dioxide (anatase) nanocrystals in vacuum and humid environments. In vacuum, the nanocrystals merge along their direction of approach, resulting in a polycrystalline material. By contrast, in the presence of water vapor, the nanocrystals reorient themselves and aggregate via the OA mechanism to form a single or twinned crystal. They accomplish this by creating a dynamic network of hydrogen bonds between surface hydroxyls and surface oxygens of aggregating nanocrystals. We determine that OA is dominant on surfaces that have the greatest propensity to dissociate water. Our results are consistent with experiment, are likely to be general for aqueous oxide systems, and demonstrate the critical role of solvent in nanocrystal aggregation. This work opens up new possibilities for directing nanocrystal growth to fabricate nanomaterials with desired shapes and sizes.
3. Li interactions in carbon based…
Advisors/Committee Members: Kristen Ann Fichthorn, Committee Chair/Co-Chair, Adrianus C Van Duin, Committee Chair/Co-Chair, Jorge Osvaldo Sofo, Committee Member, Milton Walter Cole, Committee Member, James David Kubicki, Committee Member.
Subjects/Keywords: Computational Chemistry; ReaxFF Reactive Force Fields; Fluid/Solid Interfaces; Titania-Water Interactions; Li/C ReaxFF
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APA ·
Chicago ·
MLA ·
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CSE |
Export
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Manager
APA (6th Edition):
Raju, M. (2015). Applications of Molecular Dynamics, Monte Carlo and Metadynamics Simulations using ReaxFF Reactive Force Fields to Fluid/Solid Interfaces. (Thesis). Penn State University. Retrieved from https://submit-etda.libraries.psu.edu/catalog/23853
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Chicago Manual of Style (16th Edition):
Raju, Muralikrishna. “Applications of Molecular Dynamics, Monte Carlo and Metadynamics Simulations using ReaxFF Reactive Force Fields to Fluid/Solid Interfaces.” 2015. Thesis, Penn State University. Accessed January 27, 2021.
https://submit-etda.libraries.psu.edu/catalog/23853.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
MLA Handbook (7th Edition):
Raju, Muralikrishna. “Applications of Molecular Dynamics, Monte Carlo and Metadynamics Simulations using ReaxFF Reactive Force Fields to Fluid/Solid Interfaces.” 2015. Web. 27 Jan 2021.
Vancouver:
Raju M. Applications of Molecular Dynamics, Monte Carlo and Metadynamics Simulations using ReaxFF Reactive Force Fields to Fluid/Solid Interfaces. [Internet] [Thesis]. Penn State University; 2015. [cited 2021 Jan 27].
Available from: https://submit-etda.libraries.psu.edu/catalog/23853.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Council of Science Editors:
Raju M. Applications of Molecular Dynamics, Monte Carlo and Metadynamics Simulations using ReaxFF Reactive Force Fields to Fluid/Solid Interfaces. [Thesis]. Penn State University; 2015. Available from: https://submit-etda.libraries.psu.edu/catalog/23853
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Penn State University
11.
Sun, Zhongyao.
Analysis and Logical Modeling of Biological Signaling Transduction Networks.
Degree: 2015, Penn State University
URL: https://submit-etda.libraries.psu.edu/catalog/25268
► The study of network theory and its application span across a multitude of seemingly disparate fields of science and technology: computer science, biology, social science,…
(more)
▼ The study of network theory and its application span across a multitude of seemingly disparate fields of science and technology: computer science, biology, social science, linguistics, etc. It is the intrinsic similarities embedded in the entities and the way they interact with one another in these systems that link them together.
In this dissertation, I present from both the aspect of theoretical analysis and the aspect of application three projects, which primarily focus on signal transduction networks in biology. In these projects, I assembled a network model through extensively perusing literature, performed model-based simulations and validation, analyzed network topology, and proposed a novel network measure. The application of network modeling to the system of stomatal opening in plants revealed a fundamental question about the process that has been left unanswered in decades. The novel measure of the redundancy of signal transduction networks with Boolean dynamics by calculating its maximum node-independent elementary signaling mode set accurately predicts the effect of single node knockout in such signaling processes. The three projects as an organic whole advance the understanding of a real system as well as the behavior of such network models, giving me an opportunity to take a glimpse at the dazzling facets of the immense world of network science.
Advisors/Committee Members: Reka Z Albert, Dissertation Advisor/Co-Advisor, Reka Z Albert, Committee Chair/Co-Chair, Dezhe Jin, Committee Member, Jorge Osvaldo Sofo, Committee Member, John Fricks, Committee Member.
Subjects/Keywords: network science; biological networks; discrete dynamics; Boolean network; system biology; network modeling; signal transduction
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APA ·
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MLA ·
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CSE |
Export
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APA (6th Edition):
Sun, Z. (2015). Analysis and Logical Modeling of Biological Signaling Transduction Networks. (Thesis). Penn State University. Retrieved from https://submit-etda.libraries.psu.edu/catalog/25268
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Chicago Manual of Style (16th Edition):
Sun, Zhongyao. “Analysis and Logical Modeling of Biological Signaling Transduction Networks.” 2015. Thesis, Penn State University. Accessed January 27, 2021.
https://submit-etda.libraries.psu.edu/catalog/25268.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
MLA Handbook (7th Edition):
Sun, Zhongyao. “Analysis and Logical Modeling of Biological Signaling Transduction Networks.” 2015. Web. 27 Jan 2021.
Vancouver:
Sun Z. Analysis and Logical Modeling of Biological Signaling Transduction Networks. [Internet] [Thesis]. Penn State University; 2015. [cited 2021 Jan 27].
Available from: https://submit-etda.libraries.psu.edu/catalog/25268.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Council of Science Editors:
Sun Z. Analysis and Logical Modeling of Biological Signaling Transduction Networks. [Thesis]. Penn State University; 2015. Available from: https://submit-etda.libraries.psu.edu/catalog/25268
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Penn State University
12.
Liang, Jing.
Hybrid magnetic/semiconductor nanowires: synthesis and characterization.
Degree: 2012, Penn State University
URL: https://submit-etda.libraries.psu.edu/catalog/16140
► Hybrid magnetic/semiconductor structures are of current interest for their potential in spintronic applications. Within this context, hybrid structures in the nanowire geometry are novel candidates…
(more)
▼ Hybrid magnetic/semiconductor structures are of current interest for their potential in spintronic applications. Within this context, hybrid structures in the nanowire geometry are novel candidates for room temperature spintronic devices with integrated ferromagnetic wrap-around contacts. Progress towards spin injection in quasi-one-dimensional channel provides a strong motivation for my work on hybrid ferromagnetic/semiconductor nanowires.
This thesis covers the growth, structural characterization and magnetotransport behavior of single GaAs/MnAs core/shell nanowires. First, an introductory chapter will be presented with the purpose of motivating my work and presenting highlights of past work in the field. This is followed by an overview of the techniques that were used in my experiments. Then, in the following chapters, I discuss the experiments we carried out.
The first set of experiments investigated the catalyst-free growth of GaAs nanowires and structural characterization of single nanowires. GaAs nanowires were grown using the molecular beam epitaxy (MBE) technique. Detailed transmission electron microscopy (TEM) analysis showed that GaAs nanowires are mostly in zinc-blende (ZB) phase, with segments of wurtzite (WZ) phases. Growth direction was identified as the [111] direction. Nanowires have six facets belonging to 110 family. Raman spectroscopy confirmed the coexistence of two phases. Qualitative analysis was given on the shifts of TO and LO modes corresponding to both phases.
The second set of experiments focused on synthesis and structural characterization of GaAs/MnAs core/shell nanowires using catalyst-free MBE growth technique. In additional to structural characterizations, we used local chemical analysis such as electron energy loss spectroscopy to confirm the shell composition. Cross-sectional TEM samples were prepared using a focused ion beam (FIB) system. The epitaxial relationship between the GaAs core and the MnAs shell was identified for both ZB and WZ GaAs cores. We obtained the MnAs easy axis orientations from the crystal orientations on both ZB and WZ GaAs cores. This is critical for understanding the magnetization dynamics in the ferromagnetic MnAs shell.
In the last set of experiments, we investigated the transport properties of single GaAs/MnAs core/shell nanowires. Four-probe measurements were carried out on nanowires with FIB-deposited Pt contacts. We studied nanowire resistance as a function of temperature (1 K - 350 K) and magnetic field (up to 140 kOe) along two orthogonal orientations. In the low field range, we observed anisotropic magnetoresistance (AMR). Magpar micromagnetic simulations in combination with the AMR effect proved to be a useful tool for studying the magnetization reversal process in ferromagnetic MnAs nanoshells. The striking, non-saturating, negative magnetoresistance was investigated in detail. Finally, possible mechanisms corresponding to different temperature ranges will be presented.
Advisors/Committee Members: Nitin Samarth, Dissertation Advisor/Co-Advisor, Nitin Samarth, Committee Chair/Co-Chair, Jorge Osvaldo Sofo, Committee Member, Qi Li, Committee Member, Suman Datta, Committee Member.
Subjects/Keywords: core/shell nanowire; spintronics; AMR effect; catalyst-free
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APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Liang, J. (2012). Hybrid magnetic/semiconductor nanowires: synthesis and characterization. (Thesis). Penn State University. Retrieved from https://submit-etda.libraries.psu.edu/catalog/16140
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Chicago Manual of Style (16th Edition):
Liang, Jing. “Hybrid magnetic/semiconductor nanowires: synthesis and characterization.” 2012. Thesis, Penn State University. Accessed January 27, 2021.
https://submit-etda.libraries.psu.edu/catalog/16140.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
MLA Handbook (7th Edition):
Liang, Jing. “Hybrid magnetic/semiconductor nanowires: synthesis and characterization.” 2012. Web. 27 Jan 2021.
Vancouver:
Liang J. Hybrid magnetic/semiconductor nanowires: synthesis and characterization. [Internet] [Thesis]. Penn State University; 2012. [cited 2021 Jan 27].
Available from: https://submit-etda.libraries.psu.edu/catalog/16140.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Council of Science Editors:
Liang J. Hybrid magnetic/semiconductor nanowires: synthesis and characterization. [Thesis]. Penn State University; 2012. Available from: https://submit-etda.libraries.psu.edu/catalog/16140
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Penn State University
13.
Cheng, Zhigang.
Thermodynamic Properties of Helium in Porous Media.
Degree: 2013, Penn State University
URL: https://submit-etda.libraries.psu.edu/catalog/17507
► The first credible experimental hint of non-classical rotational inertia (NCRI) or supersolidity was reported in 2004 in a torsional oscillator experiment of solid 4He confined…
(more)
▼ The first credible experimental hint of non-classical rotational inertia (NCRI) or supersolidity was reported in 2004 in a torsional oscillator experiment of solid 4He confined in Vycor. Since then numerous studies on the possible novel
state have been carried out. While it was shown very recently that the observed drop in the resonant period of the torsional oscillators housing solid helium which was interpreted as a signature of NCRI is more likely a mechanical phenomenon other than a real phase transition, a number of interesting properties of solid 4He have been observed during the last decade in many laboratories. These newly discovered results include a shear modulus anomaly, dc flow through solid helium and a heat capacity peak. Most of these studies focus on bulk crystalline solid 4He. This dissertation focuses on the study of thermodynamic properties of helium in porous media.
We have measured the heat capacity of solid 4He grown in aerogel and Vycor. For solid 4He in aerogel, the dependences of heat capacity on pressure and 3He concentration have been systematically studied. We found evidence that 3He atoms tend to reside in the vicinity of silica strands as temperature is decreased forming a 3He rich region.
We have also carried out measurements of thermal conductivity of solid 4He embedded in Vycor. The thermal conductivity of Vycor is not significantly changed with the infusion of solid helium. Interestingly, the infusion of liquid 4He in Vycor pores results in a three-fold reduction in thermal conductivity below 0.5 K. The introduction of superfluid 4He films and liquid 3He into the Vycor pores also results in the reduction of thermal conductivity. We propose a model suggesting the origin of the reduction is the presence of hydrodynamic slow sound modes in liquid 4He, as well as in superfluid 4He films and liquid 3He. The slow sound modes facilitate the quantum tunneling of two-level systems (TLS) in silica and dramatically increase the TLS-phonon scattering. The more modest reduction in solid helium-Vycor composite is caused by the presence of phonon excitations in solid helium which also facilitate TLS tunneling in silica.
Advisors/Committee Members: Moses Hung Wai Chan, Dissertation Advisor/Co-Advisor, Jainendra Jain, Committee Member, Thomas E Mallouk, Committee Member, Julian Decatur Maynard Jr., Committee Member, Jorge Osvaldo Sofo, Committee Member.
Subjects/Keywords: helium; heat capacity; thermal conductivity; porous media
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APA ·
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MLA ·
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CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Cheng, Z. (2013). Thermodynamic Properties of Helium in Porous Media. (Thesis). Penn State University. Retrieved from https://submit-etda.libraries.psu.edu/catalog/17507
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Chicago Manual of Style (16th Edition):
Cheng, Zhigang. “Thermodynamic Properties of Helium in Porous Media.” 2013. Thesis, Penn State University. Accessed January 27, 2021.
https://submit-etda.libraries.psu.edu/catalog/17507.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
MLA Handbook (7th Edition):
Cheng, Zhigang. “Thermodynamic Properties of Helium in Porous Media.” 2013. Web. 27 Jan 2021.
Vancouver:
Cheng Z. Thermodynamic Properties of Helium in Porous Media. [Internet] [Thesis]. Penn State University; 2013. [cited 2021 Jan 27].
Available from: https://submit-etda.libraries.psu.edu/catalog/17507.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Council of Science Editors:
Cheng Z. Thermodynamic Properties of Helium in Porous Media. [Thesis]. Penn State University; 2013. Available from: https://submit-etda.libraries.psu.edu/catalog/17507
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Penn State University
14.
Kim, Sung-yup.
Development Of A Reaxff Reactive Force Field For Titanium Dioxide/ Water Systems And Its Applications To Etching, Nanoparticles With Organic Solvents And Ion Adsorptions On Nanocrystalline Surfaces.
Degree: 2013, Penn State University
URL: https://submit-etda.libraries.psu.edu/catalog/16976
► A new ReaxFF reactive force field has been developed to describe reactions in the Ti-O-H system. The ReaxFF force field parameters have been fitted to…
(more)
▼ A new ReaxFF reactive force field has been developed to describe reactions in the Ti-O-H system. The ReaxFF force field parameters have been fitted to a quantum mechanical (QM) training set containing structures and energies related to bond dissociation energies, angle and dihedral distortions, and reactions between water and titanium dioxide as well as experimental crystal structures, heats of formation and bulk modulus data. Model configurations for the training set were based on DFT calculations on molecular clusters and periodic systems (both bulk crystals and surfaces). ReaxFF reproduces accurately the QM training set for structures and energetics of small clusters. ReaxFF also describes the relative energetics for rutile, brookite and anatase. The results of ReaxFF match reasonably well with those of QM for water binding energies, surface energies and H2O dissociation energy barriers. To validate this ReaxFF description, we have compared its performance against DFT/MD simulations for 1 and 3 monolayers of water interacting with a rutile (110) surface. We found agreement within 10% error between the DFT/MD and ReaxFF water dissociation levels for both coverages.
In addition to this, a new Ti-Cl force field parameter has been developed to describe reactions in Ti/O/H/Cl materials. The ReaxFF force field parameters are fitted against a quantum mechanical (QM) training set containing structures and energies related to bond dissociations, angle and dihedral distortions, and reactions between titanium and chlorine gases as well as heats of formation of TiClx crystals. These newly developed Ti-Cl force field parameters were combined with the recently developed Ti-O-H force field. ReaxFF accurately reproduces the QM training set for structures and energetics of small clusters and TiClx crystals. This force field was applied to etching simulations for titanium metal and titanium dioxide with chlorine and hydrogen chloride gases. In the etching simulations, titanium and titanium dioxide slab models with chlorine and hydrogen chloride gases were used in molecular dynamics simulations. The etching ratio between HCl and Cl2 are compared to experimental results and satisfactory results are obtained, indicating that this ReaxFF extension provides a useful tool for studying the atomistic-scale details of the etching process.
In addition, simulations of TiO2 (both rutile and anatase) nanoparticles with water, methanol and formic acid were conducted by combining C parameter with the Ti/O/H parameters to investigate the characteristic behavior of reactivity to these organic solvents. The force field was validated by comparing water dissociative adsorption percentage and bond length between Na and O with DFT and experimental results. In the simulations, 1 nm rutile and anatase nanoparticles with water, methanol and formic acid were used, respectively. The numbers of attached hydroxyl with time and nanoparticles distortion levels are presented. We found that the rutile nanoparticle is more reactive than the anatase nanoparticle…
Advisors/Committee Members: Adrianus C Van Duin, Dissertation Advisor/Co-Advisor, James David Kubicki, Committee Chair/Co-Chair, Richard A Yetter, Committee Member, Donghai Wang, Committee Member, Jorge Osvaldo Sofo, Committee Member.
Subjects/Keywords: ReaxFF; Reactive force field; titanium dioxide; nanoparticle
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APA (6th Edition):
Kim, S. (2013). Development Of A Reaxff Reactive Force Field For Titanium Dioxide/ Water Systems And Its Applications To Etching, Nanoparticles With Organic Solvents And Ion Adsorptions On Nanocrystalline Surfaces. (Thesis). Penn State University. Retrieved from https://submit-etda.libraries.psu.edu/catalog/16976
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Chicago Manual of Style (16th Edition):
Kim, Sung-yup. “Development Of A Reaxff Reactive Force Field For Titanium Dioxide/ Water Systems And Its Applications To Etching, Nanoparticles With Organic Solvents And Ion Adsorptions On Nanocrystalline Surfaces.” 2013. Thesis, Penn State University. Accessed January 27, 2021.
https://submit-etda.libraries.psu.edu/catalog/16976.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
MLA Handbook (7th Edition):
Kim, Sung-yup. “Development Of A Reaxff Reactive Force Field For Titanium Dioxide/ Water Systems And Its Applications To Etching, Nanoparticles With Organic Solvents And Ion Adsorptions On Nanocrystalline Surfaces.” 2013. Web. 27 Jan 2021.
Vancouver:
Kim S. Development Of A Reaxff Reactive Force Field For Titanium Dioxide/ Water Systems And Its Applications To Etching, Nanoparticles With Organic Solvents And Ion Adsorptions On Nanocrystalline Surfaces. [Internet] [Thesis]. Penn State University; 2013. [cited 2021 Jan 27].
Available from: https://submit-etda.libraries.psu.edu/catalog/16976.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Council of Science Editors:
Kim S. Development Of A Reaxff Reactive Force Field For Titanium Dioxide/ Water Systems And Its Applications To Etching, Nanoparticles With Organic Solvents And Ion Adsorptions On Nanocrystalline Surfaces. [Thesis]. Penn State University; 2013. Available from: https://submit-etda.libraries.psu.edu/catalog/16976
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Penn State University
15.
Rench, David William.
Investigation of Nanoscale Magnetic Materials and Devices.
Degree: 2013, Penn State University
URL: https://submit-etda.libraries.psu.edu/catalog/19223
► A host of fundamentally and technologically intriguing phenomena can be observed in ferromagnetic systems, ranging from Giant Magnetoresistance (GMR) to spin structures that approximate the…
(more)
▼ A host of fundamentally and technologically intriguing phenomena can be observed in ferromagnetic systems, ranging from Giant Magnetoresistance (GMR) to spin structures that approximate the non-zero entropy
state of water ice. In this dissertation, we consider systems of self-assembled MnAs nanoclusters in a doped GaAs matrix, a magnetically-doped topological insulator material, and magnetotransport devices constructed as artificial spin ices. We performed magnetic, structural, and electronic measurements in each of the projects herein to discover unique materials properties that range from new phase diagrams to electronic structure breaking and intriguing electrical characteristics that seem to defy the symmetry of the system that manifests them.
We first explore the impact of co-doping a GaAs semiconductor matrix with magnetic and non-magnetic dopant ions (Mn and Be, respectively) and forcing phase separation to occur during the sample growth stage. The result of this phase-separated co-doped growth was the identification of two distinct materials classes: Type I materials, in which the phase separation produces ferromagnetic zinc blende (Mn,Ga)As nanoclusters with a narrow distribution of small diameters within a weakly Be-doped GaAs matrix, and Type II materials, in which an abrupt mixing of large NiAs-type MnAs nanoclusters and the small (Mn,Ga)As nanoclusters occurs. These two states are shown to also have accessible intermediate states in the case of a doped substrate and buffer layer. Magnetic measurements are performed to determine the dynamics of the unmixed Type I and the mixed Type II materials. Structural characterization is done at the nanoscale in a variety of instruments to precisely determine the likely growth dynamics during sample synthesis and the resultant structures. The materials are found to be superparamagnetic with 10 K (Type I) and approximately 313 K (Type II) blocking temperatures with a strong dependence on Mn content during growth determining the type of material grown.
We next discuss measurements performed on the magnetically doped topological insulator candidate material Bi2Se3:Mn. The effects of Mn doping on Bi2Se3 are explored using structural and magnetic characterization techniques and the band structure is probed using Angle-Resolved PhotoEmission Spectroscopy. The material is determined to be successfully breaking time-reversal symmetry at its surface at least partially due to its suppression of the Dirac node at the gamma point of its band structure. It also shows an interesting magnetic character wherein the bulk of the material is a low temperature ferromagnet (Tc ~ 5 K) with an in-plane easy axis and the surface exhibits ferromagnetism above 100 K with an out-of-plane easy axis.
The final project described here concerns an electrically continuous network of permalloy nanowires designed as an artificial spin ice. We discuss electrical measurements of these cleanroom-fabricated devices and compare the experimental results to micromagnetic simulations. We are…
Advisors/Committee Members: Nitin Samarth, Dissertation Advisor/Co-Advisor, Peter E Schiffer, Committee Member, Jorge Osvaldo Sofo, Committee Member, Roman Engel Herbert, Committee Member, Nitin Samarth, Committee Chair/Co-Chair.
Subjects/Keywords: Nanotechnology; magnetic; semiconductors; spintronics; spin; ice; topological; insulator
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APA (6th Edition):
Rench, D. W. (2013). Investigation of Nanoscale Magnetic Materials and Devices. (Thesis). Penn State University. Retrieved from https://submit-etda.libraries.psu.edu/catalog/19223
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Chicago Manual of Style (16th Edition):
Rench, David William. “Investigation of Nanoscale Magnetic Materials and Devices.” 2013. Thesis, Penn State University. Accessed January 27, 2021.
https://submit-etda.libraries.psu.edu/catalog/19223.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
MLA Handbook (7th Edition):
Rench, David William. “Investigation of Nanoscale Magnetic Materials and Devices.” 2013. Web. 27 Jan 2021.
Vancouver:
Rench DW. Investigation of Nanoscale Magnetic Materials and Devices. [Internet] [Thesis]. Penn State University; 2013. [cited 2021 Jan 27].
Available from: https://submit-etda.libraries.psu.edu/catalog/19223.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Council of Science Editors:
Rench DW. Investigation of Nanoscale Magnetic Materials and Devices. [Thesis]. Penn State University; 2013. Available from: https://submit-etda.libraries.psu.edu/catalog/19223
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Penn State University
16.
Cooper, Brian C.
NOVEL SYNTHETIC METHODS AND CHARACTERIZATION STUDIES OF NIOBIUM-DISULFIDE IN MULTIPLE GEOMETRIES.
Degree: 2017, Penn State University
URL: https://submit-etda.libraries.psu.edu/catalog/14062bcc152
► Since the discovery of graphene, there has been a marked uptick in the rate of research conducted on layered 2D systems. Although much of this…
(more)
▼ Since the discovery of graphene, there has been a marked uptick in the rate of research
conducted on layered 2D systems. Although much of this work has focused on understanding
the properties of the semiconducting members of this group, earnest efforts towards gaining
further insight into the physical properties of the non-semiconducting members has also
been made. NbS2, a
member of the latter group, offers wide spectrum of physical behavior
for study as it undergoes multiple phase transitions from a metal at room temperature to
a dual-band superconductor a very. At room temperature this material exhibits metallic
character, while at lower temperatures in the range of 30K it undergoes a phase transition
to a charge density wave
state. It , and that is a undergoes several
state transitions within
certain temperature regimes Though the effects that quantum constraints impose on Cooper
pairs limited to planar transport have been a long established area of research, it has only
been in recent years that strides have been made into understanding the nature of quantum
confinement on dual-band superconductors.
In the contents of this thesis, I provide a thorough account of the development for a novel
technique for the synthesis of NbS2 and this technique’s evolution through the careful
characterization studies performed on the materials resulting from each successive trial. The
thesis opens with a brief introduction and relevant historical account of the study of graphene
and other 2D layered materials to provide the context from which the reader will understand
the motivation for this work.
Protocols and parameters developed from the first set of successful experiments, provided
the backbone for a reliable synthetic technique for growth of polycrystalline NbS2. The 3R
polytype of NbS2 was the overwhelmingly dominant phase within the resultant materials
grown during the first trials, but the desire to produce results rich in the 2H-NbS2 polytype
prompted a series of optimising experiments. The results of those optimizing trials, lead to
the development of a highly reliable and robust method for the synthesis of the compound.
I shall also report how these small variations to the basic experimental canon, lead to a
adaptations which could produce not only materials rich in the 2H phase of NbS2, but also NbS2 crystals exhibiting various geometries.
Advisors/Committee Members: Mauricio Terrones, Dissertation Advisor/Co-Advisor, Mauricio Terrones, Committee Chair/Co-Chair, Jorge Osvaldo Sofo, Committee Member, Nitin Samarth, Committee Member, Thomas E Mallouk, Outside Member.
Subjects/Keywords: NbS2; Layered Transition Metal Dichalcogenide
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APA (6th Edition):
Cooper, B. C. (2017). NOVEL SYNTHETIC METHODS AND CHARACTERIZATION STUDIES OF NIOBIUM-DISULFIDE IN MULTIPLE GEOMETRIES. (Thesis). Penn State University. Retrieved from https://submit-etda.libraries.psu.edu/catalog/14062bcc152
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Chicago Manual of Style (16th Edition):
Cooper, Brian C. “NOVEL SYNTHETIC METHODS AND CHARACTERIZATION STUDIES OF NIOBIUM-DISULFIDE IN MULTIPLE GEOMETRIES.” 2017. Thesis, Penn State University. Accessed January 27, 2021.
https://submit-etda.libraries.psu.edu/catalog/14062bcc152.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
MLA Handbook (7th Edition):
Cooper, Brian C. “NOVEL SYNTHETIC METHODS AND CHARACTERIZATION STUDIES OF NIOBIUM-DISULFIDE IN MULTIPLE GEOMETRIES.” 2017. Web. 27 Jan 2021.
Vancouver:
Cooper BC. NOVEL SYNTHETIC METHODS AND CHARACTERIZATION STUDIES OF NIOBIUM-DISULFIDE IN MULTIPLE GEOMETRIES. [Internet] [Thesis]. Penn State University; 2017. [cited 2021 Jan 27].
Available from: https://submit-etda.libraries.psu.edu/catalog/14062bcc152.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Council of Science Editors:
Cooper BC. NOVEL SYNTHETIC METHODS AND CHARACTERIZATION STUDIES OF NIOBIUM-DISULFIDE IN MULTIPLE GEOMETRIES. [Thesis]. Penn State University; 2017. Available from: https://submit-etda.libraries.psu.edu/catalog/14062bcc152
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Penn State University
17.
Kim, DongEung.
THERMODYNAMIC MODELING AND PREDICTION OF ELASTIC AND THERMAL EXPANSION PROPERTIES OF NI-BASE SUPERALLOYS:
APPLICATION TO NI-AL-PT-CR-HF SYSTEM WITH γ AND γ' PHASES.
Degree: 2011, Penn State University
URL: https://submit-etda.libraries.psu.edu/catalog/12437
► A computational prediction of materials performance is becoming increasingly important for the development of new materials. In the case of multicomponent materials such as Ni…
(more)
▼ A computational prediction of materials performance is becoming increasingly important for the development of new materials. In the case of multicomponent materials such as Ni base superalloys, it is very important to understand the effect of each alloying element on the phase stability and mechanical properties of the system. For last few decades, a thermodynamic modeling technique, known as the CALPHAD method (CALculation of PHAse Diagrams), has shown to be a reliable approach in calculating phase equilibria, stability and transformation in multicomponent system. At the same time, the first-principles calculations based on the density functional theory has demonstrated that it can predict the thermodynamic and mechanical properties comparable with experimental data. The first-principles calculation can also provide quantitative inputs in the CALPHAD modeling when the experimental thermochemical data is scarce.
In this dissertation, the integrated CALPHAD and first-principles calculations approach is used to study the thermodynamic, elastic and thermal expansion properties of Ni base alloys, focusing on γ+γ phases in the Ni-Al-Cr-Hf-Pt system. The available constituent binary and ternary systems in the literature are carefully reviewed and selected to combine into the quinary system. The binary systems should be well developed since binary interactions are dominant in a higher order multicomponent system. From the review of the all constituent binary system, it is found that the Al-Pt system should be remodeled since existing thermodynamic database did not include the AlPt2 and phases and the disordered fcc_A1 phase and the ordered fcc phase(L12-AlPt3) were modeled using two different Gibbs energy functions with a two-sublattice model for the ordered fcc phase, which is not consistent with other binary systems. In this work, the AlPt2 and phases are added according to new experimental observations and the four-sublattice compound energy formalism is applied to describe the ordered fcc phase, which gives the consistency with other constituent binary systems. The enthalpies of mixing of the fcc, bcc, B2 and L12 phases are calculated from the first-principles calculations using special quasirandom structures (SQS) and used to evaluate model parameters of the corresponding phases since there is no available experimental data. Then, the Ni-Al-Pt ternary system is remodeled by combining the updated Al-Pt system and other two sub-binary systems (Ni-Al and Ni-Pt) from the literature. The first-principles calculations using ternary SQS are performed to calculate the enthalpies of mixing for the fcc, bcc, B2 and L12 phases, and through this approach the challenge of scarce experimental thermochemical data for the ternary solid solution phases can be overcome. The thermodynamic database of the Ni-Al-Cr-Hf-Pt system is generated by combining the remodeled Al-Pt and Ni-Al-Pt system with the other constituent binary and ternary systems in the literature.
Apart from the highlighting the…
Advisors/Committee Members: Zi Kui Liu, Dissertation Advisor/Co-Advisor, Zi Kui Liu, Committee Chair/Co-Chair, Long Qing Chen, Committee Member, Digby D Macdonald, Committee Member, Jorge Osvaldo Sofo, Committee Member.
Subjects/Keywords: thermodynamic modeling; Ni-base superalloys; elastic property; thermal expansion property
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APA ·
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APA (6th Edition):
Kim, D. (2011). THERMODYNAMIC MODELING AND PREDICTION OF ELASTIC AND THERMAL EXPANSION PROPERTIES OF NI-BASE SUPERALLOYS:
APPLICATION TO NI-AL-PT-CR-HF SYSTEM WITH γ AND γ' PHASES. (Thesis). Penn State University. Retrieved from https://submit-etda.libraries.psu.edu/catalog/12437
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Chicago Manual of Style (16th Edition):
Kim, DongEung. “THERMODYNAMIC MODELING AND PREDICTION OF ELASTIC AND THERMAL EXPANSION PROPERTIES OF NI-BASE SUPERALLOYS:
APPLICATION TO NI-AL-PT-CR-HF SYSTEM WITH γ AND γ' PHASES.” 2011. Thesis, Penn State University. Accessed January 27, 2021.
https://submit-etda.libraries.psu.edu/catalog/12437.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
MLA Handbook (7th Edition):
Kim, DongEung. “THERMODYNAMIC MODELING AND PREDICTION OF ELASTIC AND THERMAL EXPANSION PROPERTIES OF NI-BASE SUPERALLOYS:
APPLICATION TO NI-AL-PT-CR-HF SYSTEM WITH γ AND γ' PHASES.” 2011. Web. 27 Jan 2021.
Vancouver:
Kim D. THERMODYNAMIC MODELING AND PREDICTION OF ELASTIC AND THERMAL EXPANSION PROPERTIES OF NI-BASE SUPERALLOYS:
APPLICATION TO NI-AL-PT-CR-HF SYSTEM WITH γ AND γ' PHASES. [Internet] [Thesis]. Penn State University; 2011. [cited 2021 Jan 27].
Available from: https://submit-etda.libraries.psu.edu/catalog/12437.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Council of Science Editors:
Kim D. THERMODYNAMIC MODELING AND PREDICTION OF ELASTIC AND THERMAL EXPANSION PROPERTIES OF NI-BASE SUPERALLOYS:
APPLICATION TO NI-AL-PT-CR-HF SYSTEM WITH γ AND γ' PHASES. [Thesis]. Penn State University; 2011. Available from: https://submit-etda.libraries.psu.edu/catalog/12437
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Penn State University
18.
Liu, Guoxing.
RESONANT ULTRASOUND SPECTROSCOPY AND
SOLID HELIUM RESEARCH
.
Degree: 2011, Penn State University
URL: https://submit-etda.libraries.psu.edu/catalog/12085
► Recent experiments have indicated some interesting phenomena in solid helium. We have been adapting resonant ultrasound spectroscopy (RUS), which can be used to measure all…
(more)
▼ Recent experiments have indicated some interesting phenomena in solid helium. We have been adapting resonant ultrasound spectroscopy (RUS), which can be used to measure all of a solid's elastic moduli, for use with solid helium. In the RUS technique, a cell with known geometry is attached with ultrasound drive and receive transducers so that a number (10-30) of the cell's natural frequencies may be measured; by analyzing the natural frequencies, valuable information about elastic moduli of the cell’s content (solid helium) can be gained. For RUS to work, it is essential that the normal modes of the cell be well understood. We developed a cell which will maintain robust normal modes when the cell is cycled in temperature and pressure. Normal modes of the vibration of the can fall into two distinct classes: In one class, nearly all energy is in the steel can, and the modes and natural frequencies of this group are almost the same as the empty can. However, helium inside does move with the can and slightly shifts the natural frequency. The second class only show up when there is helium inside the cell and they depend mostly on the helium properties. It was anticipated that the transducers, being outside of the can, would not be sensitive to the second class of normal modes. The plan was to determine elastic properties of helium by analyzing the small frequency shifts of the first class of normal modes. It turns out that transducers are able to determine the natural frequencies of some of the second class modes, which are much more sensitive to helium properties. A finite element method is used to track how resonance frequencies change as 4He (elastic) properties change. This is achieved by comparing the similarity of the resonance modes. We find that resonance frequencies that are sensitive to solid 4He increase by ~2% from 1 K to 2 K in our experiment. According to our calculation, this corresponds to a ~4% increase in solid 4He shear modulus. This shear modulus change could be explained using dislocation theory with appropriate parameters.
Advisors/Committee Members: Julian Decatur Maynard Jr., Dissertation Advisor/Co-Advisor, Julian Decatur Maynard Jr., Committee Chair/Co-Chair, Moses Hung Wai Chan, Committee Member, Jorge Osvaldo Sofo, Committee Member, Victor Ward Sparrow, Committee Member.
Subjects/Keywords: resonant ultrasound spectroscopy; Helium
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APA ·
Chicago ·
MLA ·
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CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Liu, G. (2011). RESONANT ULTRASOUND SPECTROSCOPY AND
SOLID HELIUM RESEARCH
. (Thesis). Penn State University. Retrieved from https://submit-etda.libraries.psu.edu/catalog/12085
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Chicago Manual of Style (16th Edition):
Liu, Guoxing. “RESONANT ULTRASOUND SPECTROSCOPY AND
SOLID HELIUM RESEARCH
.” 2011. Thesis, Penn State University. Accessed January 27, 2021.
https://submit-etda.libraries.psu.edu/catalog/12085.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
MLA Handbook (7th Edition):
Liu, Guoxing. “RESONANT ULTRASOUND SPECTROSCOPY AND
SOLID HELIUM RESEARCH
.” 2011. Web. 27 Jan 2021.
Vancouver:
Liu G. RESONANT ULTRASOUND SPECTROSCOPY AND
SOLID HELIUM RESEARCH
. [Internet] [Thesis]. Penn State University; 2011. [cited 2021 Jan 27].
Available from: https://submit-etda.libraries.psu.edu/catalog/12085.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Council of Science Editors:
Liu G. RESONANT ULTRASOUND SPECTROSCOPY AND
SOLID HELIUM RESEARCH
. [Thesis]. Penn State University; 2011. Available from: https://submit-etda.libraries.psu.edu/catalog/12085
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Penn State University
19.
Neogi, Sanghamitra.
TRANSPORT IN NONLINEAR CHAINS AND ACROSS SEVERAL CONDENSED MATTER INTERFACES
.
Degree: 2011, Penn State University
URL: https://submit-etda.libraries.psu.edu/catalog/11827
► The characteristic length scales of the materials synthesized, are becoming increasingly small with the advances in experimental techniques. Many of these microscopic structures found their…
(more)
▼ The characteristic length scales of the materials synthesized, are becoming increasingly small with the advances in experimental techniques. Many of these microscopic structures found their places in important commercial applications, while research is going on toward finding materials with even smaller length scales. The thermal loads imposed on these devices and structures create a major obstacle toward their applicability. This challenge is driving a renewed interest among researchers from various disciplines, toward the topic of thermal management. The interest in the topic of thermal transport served as the motivation for the work performed in the dissertation. More specifically, the following topics were investigated:
�egin{itemize}
item {�f Transport in One-Dimensional Nonlinear Systems:} Thermal transport in materials can be explained in terms of the motion of the heat carriers at the microscopic level, with the heat carriers typically being electrons, phonons, atoms, or molecules. However, an important and surprising situation emerges in some low dimensional model systems; the thermal conductivity diverges with system size. It was shown (Toda, 1979) that nonlinearity has an important effect in the heat transport in low dimensional systems. We investigate the transport of energy in a nonlinear one-dimensional chain. We show the spontaneous generation of solitons with the application of forcing functions at the end of the chain and study the different properties of the solitons generated in the chain.
item {�f Transport in FLuids extemdash Study of Pair Distribution Function:} Thermal transport in fluids is also diffusive in nature. The transport of heat depends on the distribution of particles in the fluid. It is well known that the two-particle distribution function can describe most of the thermodynamic properties for classical fluids in thermal equilibrium. We review the approximate integral equation theories (Percus-Yevick, Hypernetted chain approximation) to obtain the pair distribution function of classical fluids. We find that these methods are highly dependent on the choice of the thermodynamic parameters of the fluid. We solve several Lennard-Jones fluid systems with different density and temperature values and prepare a density-temperature compressibility diagram. This diagram shows the region of applicability of these theories and helps us obtain the pair distribution function for a Lennard-Jones fluid with known thermodynamic parameters. We also suggest a modification of the integral-equation theories to obtain the pair distribution functions of quantum fluids. We show how the knowledge of pair distribution function can be used to obtain various thermodynamic properties of the quantum fluid helium-4.
item {�f Thermal Transport Across Interfaces:} When thermal energy is transported from one material to another, there is a discontinuity in temperature at the interface between them. This thermal boundary resistance is known as Kapitza resistance. The scattering of phonons at interfaces is one of…
Advisors/Committee Members: Gerald Dennis Mahan, Dissertation Advisor/Co-Advisor, Gerald Dennis Mahan, Committee Chair/Co-Chair, Jorge Osvaldo Sofo, Committee Member, Jun Zhu, Committee Member, John V Badding, Committee Member.
Subjects/Keywords: Solitons; one-dimensional lattice; pair distribution function; Kapitza resistance at interfaces
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APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Neogi, S. (2011). TRANSPORT IN NONLINEAR CHAINS AND ACROSS SEVERAL CONDENSED MATTER INTERFACES
. (Thesis). Penn State University. Retrieved from https://submit-etda.libraries.psu.edu/catalog/11827
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Chicago Manual of Style (16th Edition):
Neogi, Sanghamitra. “TRANSPORT IN NONLINEAR CHAINS AND ACROSS SEVERAL CONDENSED MATTER INTERFACES
.” 2011. Thesis, Penn State University. Accessed January 27, 2021.
https://submit-etda.libraries.psu.edu/catalog/11827.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
MLA Handbook (7th Edition):
Neogi, Sanghamitra. “TRANSPORT IN NONLINEAR CHAINS AND ACROSS SEVERAL CONDENSED MATTER INTERFACES
.” 2011. Web. 27 Jan 2021.
Vancouver:
Neogi S. TRANSPORT IN NONLINEAR CHAINS AND ACROSS SEVERAL CONDENSED MATTER INTERFACES
. [Internet] [Thesis]. Penn State University; 2011. [cited 2021 Jan 27].
Available from: https://submit-etda.libraries.psu.edu/catalog/11827.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Council of Science Editors:
Neogi S. TRANSPORT IN NONLINEAR CHAINS AND ACROSS SEVERAL CONDENSED MATTER INTERFACES
. [Thesis]. Penn State University; 2011. Available from: https://submit-etda.libraries.psu.edu/catalog/11827
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Penn State University
20.
Criss, Adrienne Elizabeth.
Atmospherics effects on events measured by the Pierre Auger Observatory surface detector.
Degree: 2012, Penn State University
URL: https://submit-etda.libraries.psu.edu/catalog/13744
► The nature of ultra high energy cosmic rays, nuclear particles from outer space with energies greater than 1018 eV, is one of the big mysteries…
(more)
▼ The nature of ultra high energy cosmic rays, nuclear particles from outer space with energies greater than 10
18 eV, is one of the big mysteries of physics due to
the low flux of events that reach earth. This small flux necessitates the use of detectors with large collecting areas and excludes using satellite and balloon borne experiments which could detect cosmic rays directly. Instead, we must study the extensive air shower (EAS) caused by a primary cosmic ray as it traverses the atmosphere.
When a cosmic ray enters the earth’s atmosphere it interacts to produce pions. The pions continue to interact until the energy per particle falls below a critical threshold, roughly 2000 MeV. While the charged pions produce muons and neutrinos, the neutral pions produce electromagnetic cascades of electrons, positrons, and gamma rays. This collection of particles is known as an EAS.
The Pierre Auger Observatory was built to study these rare cosmic rays and answer fundamental questions about them, such as their origin and composition.
Located in Argentina, the Pierre Auger Observatory detects the EASs created by primary cosmic rays. Since the development of EASs is affected by the atmosphere,
it is important to understand these effects so that we can more accurately reconstruct the events. An accurate determination of the primary cosmic ray energy
leads to the ability to make more sensitive anisotropy studies, for example.
To this end, rate variations over annual and diurnal cycles are studied. We look at rate variations in comparison with atmospheric temperature and pressure. Using a modified Rayleigh analysis we show that the rate lags behind the temperature in both cases. A lag of 2 weeks is seen in the annual case; in the diurnal case a lag of 2 hours is visible. Both effects are seen at greater than a 3σ level using events with
zenith angles less than 45 degrees. From the modified Rayleigh analysis, we also obtain coefficients which are used to normalize the atmospheric parameters to the
rate. Since these coefficients measure the strength of the effect on the rate caused by that parameter, they can be used to remove the atmospheric effects. Using these atmospheric correction coefficients and phase lags, we correct the event energies. These corrections remove the spurious sinusoidal variations seen in the raw data. Redoing the analysis with the atmospheric corrected data, we find that the annual
and diurnal rates are flat within uncertainties.
This improves the upper limits on cosmic ray anisotropy in right ascension. No evidence of anisotropy is found in either the first or second harmonic over 5 differential energy bins. Anisotropy amplitudes of 1-3% are seen in the 4 ≤ E < 8
EeV and 8 EeV ≤ E energy ranges for both the first and second harmonic; the significances are less than 1.5σ in all cases though. At lower energies, the anisotropy
amplitudes are generally even lower. The significances of detections are still below 3σ.
Advisors/Committee Members: Paul Sommers, Dissertation Advisor/Co-Advisor, Paul Sommers, Committee Chair/Co-Chair, Stephane Coutu, Committee Member, Tyce De Young, Committee Member, Peter Istvan Meszaros, Committee Member, Jorge Osvaldo Sofo, Committee Member.
Subjects/Keywords: cosmic rays; ultra-high energy; Pierre Auger Observatory; atmosphere; atmospheric effects
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APA (6th Edition):
Criss, A. E. (2012). Atmospherics effects on events measured by the Pierre Auger Observatory surface detector. (Thesis). Penn State University. Retrieved from https://submit-etda.libraries.psu.edu/catalog/13744
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Chicago Manual of Style (16th Edition):
Criss, Adrienne Elizabeth. “Atmospherics effects on events measured by the Pierre Auger Observatory surface detector.” 2012. Thesis, Penn State University. Accessed January 27, 2021.
https://submit-etda.libraries.psu.edu/catalog/13744.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
MLA Handbook (7th Edition):
Criss, Adrienne Elizabeth. “Atmospherics effects on events measured by the Pierre Auger Observatory surface detector.” 2012. Web. 27 Jan 2021.
Vancouver:
Criss AE. Atmospherics effects on events measured by the Pierre Auger Observatory surface detector. [Internet] [Thesis]. Penn State University; 2012. [cited 2021 Jan 27].
Available from: https://submit-etda.libraries.psu.edu/catalog/13744.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Council of Science Editors:
Criss AE. Atmospherics effects on events measured by the Pierre Auger Observatory surface detector. [Thesis]. Penn State University; 2012. Available from: https://submit-etda.libraries.psu.edu/catalog/13744
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Penn State University
21.
Coimbatore Balram, Ajit.
Exotic emergent phenomena in the fractional quantum Hall effect.
Degree: 2016, Penn State University
URL: https://submit-etda.libraries.psu.edu/catalog/29598
► When two-dimensional electron systems are subjected to a perpendicular magnetic field, they exhibit the marvelous phenomenon known as the fractional quantum Hall effect (FQHE). This…
(more)
▼ When two-dimensional electron systems are subjected to a perpendicular magnetic field, they exhibit the marvelous phenomenon known as the fractional quantum Hall effect (FQHE). This arises as a result of the formation of composite fermions (CFs), which are bound states of electrons and an even number of vortices. The FQHE of electrons is understood as arising from the integer QHE (IQHE) of CFs. Alongside superconductivity, Bose-Einstein condensation and spin-liquids, the CF quantum fluid provides a model system for understanding strongly correlated systems and their collective behavior. Although it has been more than three decades since the experimental discovery of FQHE, the field continues to produce profound insights and pose interesting problems some of which have been addressed in this thesis.\\
A major unanswered question in the field of FQHE is the mechanism of FQHE for the 1/3
state in the second Landau leve (7/3
state). Numerical studies of this
state have brought out the following puzzle: exact diagonalization studies suggest that the ground
state and excitations of 1/3
state in the second Landau level are different from its counterpart in the lowest Landau level (LLL), while entanglement spectra of the two states point to the fact that they fall in the same universality class. Using methods from CF theory we show that the excitations of the 7/3 FQHE lie in the same universality class as those of the 1/3
state but are strongly modified due to screening by CF excitons, thereby settling the above discrepancy. \\
Armed with the exciton calculation, we illustrate that by imposing certain exclusion rules for CF excitons one can build the full spectrum of FQHE in the lowest Landau level. Equipped with the techniques to calculate the spectra of FQHE systems, we carry out an extensive study of FQHE of multi-component CFs (systems possessing degrees of freedom for eg: valley and spin degeneracy), which is applicable to FQHE in systems such as graphene, AlAs and GaAs quantum wells. We provide a comprehensive list of the possible fractions, their ground
state energies and the critical ``Zeeman'' energies for the ``spin'' transitions between the states and compare them with the experimental observations. In the lowest Landau level of graphene, we find an excellent agreement between theory and experiments. However, in the second Landau level of graphene we find an unexpected spontaneous spin polarization of CFs. We predict that there are no spin transitions to be expected in the second Landau level of graphene, a result that could be tested out in experiments. We reanalyzed some old experimental data showing excitation modes below the Zeeman energy in the vicinity of 1/3 filling of the lowest Landau level whose theoretical origin was unexplained. Using methods of exact diagonalization and CF theory we demonstrate that these modes arise as a result of formation of trions of CFs which have sub-Zeeman energy due to skyrmion-like physics.\\
In the past couple of years, the Fermi wave vector of CFs has been measured…
Advisors/Committee Members: Jainendra Jain, Dissertation Advisor/Co-Advisor, Jainendra Jain, Committee Chair/Co-Chair, Nitin Samarth, Committee Member, Jorge Osvaldo Sofo, Committee Member, Thomas E Mallouk, Committee Member.
Subjects/Keywords: FQHE; topological phases; composite fermions
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APA ·
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MLA ·
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Export
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APA (6th Edition):
Coimbatore Balram, A. (2016). Exotic emergent phenomena in the fractional quantum Hall effect. (Thesis). Penn State University. Retrieved from https://submit-etda.libraries.psu.edu/catalog/29598
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Chicago Manual of Style (16th Edition):
Coimbatore Balram, Ajit. “Exotic emergent phenomena in the fractional quantum Hall effect.” 2016. Thesis, Penn State University. Accessed January 27, 2021.
https://submit-etda.libraries.psu.edu/catalog/29598.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
MLA Handbook (7th Edition):
Coimbatore Balram, Ajit. “Exotic emergent phenomena in the fractional quantum Hall effect.” 2016. Web. 27 Jan 2021.
Vancouver:
Coimbatore Balram A. Exotic emergent phenomena in the fractional quantum Hall effect. [Internet] [Thesis]. Penn State University; 2016. [cited 2021 Jan 27].
Available from: https://submit-etda.libraries.psu.edu/catalog/29598.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Council of Science Editors:
Coimbatore Balram A. Exotic emergent phenomena in the fractional quantum Hall effect. [Thesis]. Penn State University; 2016. Available from: https://submit-etda.libraries.psu.edu/catalog/29598
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Penn State University
22.
Engstrom, Tyler Adam.
Topics in solid-state astrophysics: magnetized neutron star crusts and multicomponent crusts/white dwarfs.
Degree: 2015, Penn State University
URL: https://submit-etda.libraries.psu.edu/catalog/27294
► Two research endeavors are described in this dissertation; both undertake problems in solid-state astrophysics, which is a branch of solid-state physics concerning the extreme conditions…
(more)
▼ Two research endeavors are described in this dissertation; both undertake problems in solid-
state astrophysics, which is a branch of solid-
state physics concerning the extreme conditions found within white dwarfs and the solid crusts of neutron stars. As much of our knowledge about these compact objects comes from observation of astrophysical phenomena, Chapter 1 is devoted to the phenomena, and how they can be exploited as material property probes. Several of the most interesting phenomena involve the enormous magnetic fields (B>10
12 gauss) harbored by many neutron stars, and the interaction between these fields and the charged particles within the solid crust. Accordingly, Chapter 2 reviews some theory of strongly-magnetized electrons, which both sets the stage for Chapter 3, and (hopefully) serves as a useful reference for future research. Let it now be made clear that this dissertation focuses exclusively on the ``outer crusts,'' of neutron stars, where no free neutrons are present (rho<4x10
11 g/cc), and the similarly-composed interiors of white dwarfs, which have central densities ~10
7 g/cc. For the most part we specialize to even lower densities.
In Chapter 3, static and dynamic properties of low density (rho<10
6 g/cc) outer envelopes of neutron stars are calculated within the nonlinear magnetic Thomas-Fermi model, assuming degenerate electrons. A novel domain decomposition enables proper description of lattice symmetry and may be seen as a prototype for the general class of problems involving nonlinear charge screening of periodic, quasi-low-dimensionality structures, e.g. liquid crystals. We describe a scalable implementation of the method using Hypre. Over the density range considered, the effective shear modulus appears to be a factor of approximately 20 larger than in the linearly-screened Coulomb crystal model, which could have implications for observables related to astroseismology as well as low temperature phonon-mediated thermal conductivity. Other findings include incipient c'<0 elastic instabilities for both bcc and fcc lattices, reminiscent of the situation in some light actinides, and suggestive of a symmetry-lowering transition to a tetragonal or orthorhombic lattice.
Chapter 4 describes a systematic search for multicomponent crystal structures, carried out for five different ternary systems of nuclei in a polarizable background of electrons, representative of accreted neutron star crusts and some white dwarfs. Candidate structures are ``bred'' by a genetic algorithm, and optimized at constant pressure under the assumption of linear response (Thomas-Fermi) charge screening. Subsequent phase equilibria calculations reveal eight distinct crystal structures in the T=0 bulk phase diagrams, five of which are complicated multinary structures not before predicted in the context of compact object astrophysics. Frequent instances of geometrically similar but compositionally distinct phases give insight into structural preferences of systems with pairwise Yukawa interactions, including…
Advisors/Committee Members: Vincent Henry Crespi, Dissertation Advisor/Co-Advisor, Vincent Henry Crespi, Committee Chair/Co-Chair, Jorge Osvaldo Sofo, Committee Member, Benjamin Owen, Committee Member, James Joseph Brannick, Committee Member, George Pavlov, Special Member.
Subjects/Keywords: neutron stars; white dwarfs; dense matter; magnetic fields; numerical methods
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APA ·
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MLA ·
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Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Engstrom, T. A. (2015). Topics in solid-state astrophysics: magnetized neutron star crusts and multicomponent crusts/white dwarfs. (Thesis). Penn State University. Retrieved from https://submit-etda.libraries.psu.edu/catalog/27294
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Chicago Manual of Style (16th Edition):
Engstrom, Tyler Adam. “Topics in solid-state astrophysics: magnetized neutron star crusts and multicomponent crusts/white dwarfs.” 2015. Thesis, Penn State University. Accessed January 27, 2021.
https://submit-etda.libraries.psu.edu/catalog/27294.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
MLA Handbook (7th Edition):
Engstrom, Tyler Adam. “Topics in solid-state astrophysics: magnetized neutron star crusts and multicomponent crusts/white dwarfs.” 2015. Web. 27 Jan 2021.
Vancouver:
Engstrom TA. Topics in solid-state astrophysics: magnetized neutron star crusts and multicomponent crusts/white dwarfs. [Internet] [Thesis]. Penn State University; 2015. [cited 2021 Jan 27].
Available from: https://submit-etda.libraries.psu.edu/catalog/27294.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Council of Science Editors:
Engstrom TA. Topics in solid-state astrophysics: magnetized neutron star crusts and multicomponent crusts/white dwarfs. [Thesis]. Penn State University; 2015. Available from: https://submit-etda.libraries.psu.edu/catalog/27294
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Penn State University
23.
Zhou, Bicheng.
A computational study of the effects of alloying elements on the thermodynamic and diffusion properties of Mg alloys.
Degree: 2015, Penn State University
URL: https://submit-etda.libraries.psu.edu/catalog/27522
► In recent years, magnesium (Mg) alloys have received an increasing interest due to their low density, earth abundance, high specific strength, and good castability. These…
(more)
▼ In recent years, magnesium (Mg) alloys have received an increasing interest due to their low density, earth abundance, high specific strength, and good castability. These properties make Mg alloys attractive for automotive, aerospace, and other light-weight structural applications. The majority of Mg alloys derives their mechanical properties from precipitation hardening, while the study of precipitation process demands accurate thermodynamic and kinetic (diffusion) properties.
In this dissertation, two computational techniques, the CALculation of PHAse Diagram (CALPHAD) modeling and first-principles calculations, have been employed to understand the effects of various alloying elements on the thermodynamic and diffusion properties of Mg alloys. Thermodynamics and phase stability of two Mg ternary alloy systems, Mg-Sn-Sr and Mg-Ce-Sn, have been investigated through use of the CALPHAD modeling technique. They have the potential to be used for high-temperature applications due to the highly stable Mg2Sn as the main precipitate phase. The thermodynamic modeling is supplemented by finite temperature first-principles calculations based on density functional theory (DFT) using the quasi-harmonic phonon calculations and the Debye model with inputs from first-principles calculations. The associate solution model is used to describe the short-range ordering behavior in the liquid phases of these two alloy systems.
To better understand the diffusion properties of Mg alloys, the self-diffusion and solute (impurity) diffusion coefficients of 61 alloying elements in hcp Mg are calculated from first-principles by combining transition
state theory and an 8-frequency model. The minimum energy pathways and the saddle point configurations during solute migration are calculated with the climbing image nudged elastic band method. Vibrational properties are obtained using the quasi-harmonic Debye model with inputs from first-principles calculations. An improved generalized gradient approximation of PBEsol is used in the present first-principles calculations, which is able to well describe both vacancy formation energies and vibrational properties. It is found that the solute diffusion coefficients in dilute hcp Mg are roughly inversely proportional to bulk modulus of the dilute alloys, which reflects the solutes’ bonding to Mg. Transition metal elements with d electrons show strong interactions with Mg and have large diffusion activation energies. Correlation effects are not negligible for solutes Ca, Na, Sr, Se, Te, Y, and early rare earths La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, in which the direct solute migration barriers are much smaller than the solvent (Mg) migration barriers. Solutes with large atomic size have lower migration barriers due to large local strain in the Mg matrix. Calculated diffusion coefficients are in remarkable agreement with available experimental data in the literature. The calculated diffusion coefficients can be used as the input in mesoscale simulations like phase field and finite element simulations or be used to…
Advisors/Committee Members: Zi Kui Liu, Dissertation Advisor/Co-Advisor, Zi Kui Liu, Committee Chair/Co-Chair, Long Qing Chen, Committee Member, Jorge Osvaldo Sofo, Committee Member, Tarasankar Debroy, Committee Member.
Subjects/Keywords: Mg alloys; thermodynamics; diffusion; thermodynamic modeling; CALPHAD; first-principles calculations; DFT; kinetics
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APA ·
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MLA ·
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Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Zhou, B. (2015). A computational study of the effects of alloying elements on the thermodynamic and diffusion properties of Mg alloys. (Thesis). Penn State University. Retrieved from https://submit-etda.libraries.psu.edu/catalog/27522
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Chicago Manual of Style (16th Edition):
Zhou, Bicheng. “A computational study of the effects of alloying elements on the thermodynamic and diffusion properties of Mg alloys.” 2015. Thesis, Penn State University. Accessed January 27, 2021.
https://submit-etda.libraries.psu.edu/catalog/27522.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
MLA Handbook (7th Edition):
Zhou, Bicheng. “A computational study of the effects of alloying elements on the thermodynamic and diffusion properties of Mg alloys.” 2015. Web. 27 Jan 2021.
Vancouver:
Zhou B. A computational study of the effects of alloying elements on the thermodynamic and diffusion properties of Mg alloys. [Internet] [Thesis]. Penn State University; 2015. [cited 2021 Jan 27].
Available from: https://submit-etda.libraries.psu.edu/catalog/27522.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Council of Science Editors:
Zhou B. A computational study of the effects of alloying elements on the thermodynamic and diffusion properties of Mg alloys. [Thesis]. Penn State University; 2015. Available from: https://submit-etda.libraries.psu.edu/catalog/27522
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Penn State University
24.
Zacherl, Chelsey Leanne.
A computational investigation of the effect of alloying elements on the thermodynamic and diffusion properties of fcc Ni alloys, with application to the creep rate of dilute Ni-X alloys.
Degree: 2012, Penn State University
URL: https://submit-etda.libraries.psu.edu/catalog/15158
► Ni-base superalloys have become ubiquitous in the materials science community in the past half-century because of their superior ability to resist chemical and mechanical degradation…
(more)
▼ Ni-base superalloys have become ubiquitous in the materials science community in the past half-century because of their superior ability to resist chemical and mechanical degradation at temperature upwards of 70 % of their melting temperature. Future generations of Ni-base superalloys with increased service lifetimes and higher efficiencies will require the development of more complex, multi-component alloys carefully engineered to meet specific materials properties specifications, such as high temperature creep resistance. This can only come from an intimate knowledge of the exact effects of each individual alloying element on the thermodynamic and kinetic properties of the Ni-base superalloys. In this dissertation, two computational techniques have been employed to understand the alloying effects of various transition elements in Ni and its alloys. Thermodynamics and phase stability has been investigated through use of the CALculation of PHAse Diagram (CALPHAD) modeling technique, supplemented by first-principles calculations based on density functional theory (DFT). To better understand the kinetics involved in materials transport, the self-diffusion in ferromagnetic fcc Ni is calculated by first-principles, followed by a systematic investigation of the effects of 26 alloying elements on dilute Ni-rich binary alloys. Mechanisms causing specific diffusion behavior are explored, and the usefullness of such a database of knowledge is demonstrated by applying the generated data to a secondary creep rate model to show how each alloying element affects the creep behavior of the dilute Ni alloy systems. Finally, the next frontier of diffusion coefficient calculations by first-principles is explored by extending the calculation to non-dilute impurity concentrations, employing the fourteen-frequency model applied to the Ni-Al system.
To aid in the process of narrowing down the large composition space for the design of future Ni-base superalloys, a thermodynamic model using the CALPHAD approach is developed, where Gibbs energy functions of individual phases are parameterized based on fittings to experimentally measured phase equilibria or thermochemical data and computationally predicted thermochemical data. Multi-component Ni-base superalloys can be accurately described within the CALPHAD approach through the extrapolation of the Gibbs energy functions of the simpler sub-systems which are modeled where experimental and computational data is usually more abundant. The Re-Y and Re-Ti systems, integral binary alloy systems in the Ni-base superalloy database, are modeled in the present work. Since little thermochemical data was available for either system, first-principles calculations were used to improve the thermodynamic models of the solid solution phases and the compounds. Both phase diagrams show excellent agreement with available experimental phase equilibria data. To further demonstrate the utility of first-principles calculations, an investigation on the phase stability of the ReTi compound is performed,…
Advisors/Committee Members: Zi Kui Liu, Dissertation Advisor/Co-Advisor, Zi Kui Liu, Committee Chair/Co-Chair, Long Qing Chen, Committee Member, Paul Raymond Howell, Committee Member, Jorge Osvaldo Sofo, Committee Member.
Subjects/Keywords: Ni-base superalloys; thermodynamic modeling; self-diffusion; impurity diffusion; non-dilute impurity diffusion; first-principles
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APA ·
Chicago ·
MLA ·
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CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Zacherl, C. L. (2012). A computational investigation of the effect of alloying elements on the thermodynamic and diffusion properties of fcc Ni alloys, with application to the creep rate of dilute Ni-X alloys. (Thesis). Penn State University. Retrieved from https://submit-etda.libraries.psu.edu/catalog/15158
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Chicago Manual of Style (16th Edition):
Zacherl, Chelsey Leanne. “A computational investigation of the effect of alloying elements on the thermodynamic and diffusion properties of fcc Ni alloys, with application to the creep rate of dilute Ni-X alloys.” 2012. Thesis, Penn State University. Accessed January 27, 2021.
https://submit-etda.libraries.psu.edu/catalog/15158.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
MLA Handbook (7th Edition):
Zacherl, Chelsey Leanne. “A computational investigation of the effect of alloying elements on the thermodynamic and diffusion properties of fcc Ni alloys, with application to the creep rate of dilute Ni-X alloys.” 2012. Web. 27 Jan 2021.
Vancouver:
Zacherl CL. A computational investigation of the effect of alloying elements on the thermodynamic and diffusion properties of fcc Ni alloys, with application to the creep rate of dilute Ni-X alloys. [Internet] [Thesis]. Penn State University; 2012. [cited 2021 Jan 27].
Available from: https://submit-etda.libraries.psu.edu/catalog/15158.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Council of Science Editors:
Zacherl CL. A computational investigation of the effect of alloying elements on the thermodynamic and diffusion properties of fcc Ni alloys, with application to the creep rate of dilute Ni-X alloys. [Thesis]. Penn State University; 2012. Available from: https://submit-etda.libraries.psu.edu/catalog/15158
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Penn State University
25.
Wang, Yi.
A FIRST-PRINCIPLES STUDY OF STACKING FAULTS AND LONG PERIODIC STACKING ORDER STRUCTURES IN MG AND MG ALLOYS.
Degree: 2013, Penn State University
URL: https://submit-etda.libraries.psu.edu/catalog/19843
► Since the main challenges in developing Mg alloys are to increase their strength, ductility, as well as stability at high temperatures, it is crucial to…
(more)
▼ Since the main challenges in developing Mg alloys are to increase their strength, ductility, as well as stability at high temperatures, it is crucial to understand the fundamental properties which affect their mechanical properties. Formation of stacking faults is fundamental in deformation of materials with the hcp structure such as Mg and Ti alloys, affecting core structures and the mobility of dislocations, twinnability and ductility, and creep rate. Moreover, long periodic stacking order (LPSO) structures, such as 6H, 10H, 14H, 18R and 24R, play significant roles in enhancing the mechanical properties of Mg alloys and have been largely investigated separately.
In the present work, contributions of stacking faults, LPSOs and alloying elements to the formation energy, elastic, electronic and phonon properties of Mg and Mg alloys are investigated through the first-principles calculations.
In pure Mg, the connections among stacking faults and LPSOs are discussed. Three typical basal-plane stacking faults, i.e. growth fault (I1), deformation fault (I2) and extrinsic fault (EF), are investigated, showing that the stacking fault energy increases in the order of I1 < I2 < EF. Moreover, through the electron localization morphology, electronic structures of these three stacking faults are revealed in terms of deformation electron density (Δρ) and electron localization function (ELF). These results yield a quantitative description of charge transfer between atoms in and out of the stacking faults. We also obtain a brief physical correlation between stacking fault energy and the difference of Δρ and ELF between the fault planes and the non-fault planes. Furthermore, through detailed investigations of deformation electron density, we show that the electron structures of 10H, 14H, 18R and 24R LPSO structures in Mg originate from those of deformation stacking faults in Mg, and their formation energies can be scaled with respect to formation energy and the number of layers of deformation stacking faults, while the electron structure and formation energy of the 6H LPSO structure are between those of deformation and growth stacking faults. The simulated images of high resolution transmission electron microscopy compare well with experimental observed ones. In the end, effects of fault layers in SFs and LPSOs on the local phonon density of states and vibrational entropy are discussed together with their specific electronic structures.
In the binary Mg-X alloys, contributions of 17 alloying elements to the energy and the bond structure of growth, deformation and extrinsic faults are investigated. In view of electron localization morphology, the bonding structure of Mg around the fault plane can be recognized as the HCP-FCC transformations in short-range. Together with the specific electron structure of each alloying element, it has been confirmed that bond strength of the fault planes are strengthened by FCC-Al and HCP-Zn since tetrahedrons around alloying elements have more electron density. Taking Gd and Y as…
Advisors/Committee Members: Zi Kui Liu, Dissertation Advisor/Co-Advisor, Zi Kui Liu, Committee Chair/Co-Chair, Long Qing Chen, Committee Member, Jorge Osvaldo Sofo, Committee Member, Suzanne E Mohney, Committee Member, Suveen N Mathaudhu, Special Member.
Subjects/Keywords: Stacking fault; Long periodic stacking order (LPSO); Deformation electron density; Atomic array/cluster
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APA ·
Chicago ·
MLA ·
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CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Wang, Y. (2013). A FIRST-PRINCIPLES STUDY OF STACKING FAULTS AND LONG PERIODIC STACKING ORDER STRUCTURES IN MG AND MG ALLOYS. (Thesis). Penn State University. Retrieved from https://submit-etda.libraries.psu.edu/catalog/19843
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Chicago Manual of Style (16th Edition):
Wang, Yi. “A FIRST-PRINCIPLES STUDY OF STACKING FAULTS AND LONG PERIODIC STACKING ORDER STRUCTURES IN MG AND MG ALLOYS.” 2013. Thesis, Penn State University. Accessed January 27, 2021.
https://submit-etda.libraries.psu.edu/catalog/19843.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
MLA Handbook (7th Edition):
Wang, Yi. “A FIRST-PRINCIPLES STUDY OF STACKING FAULTS AND LONG PERIODIC STACKING ORDER STRUCTURES IN MG AND MG ALLOYS.” 2013. Web. 27 Jan 2021.
Vancouver:
Wang Y. A FIRST-PRINCIPLES STUDY OF STACKING FAULTS AND LONG PERIODIC STACKING ORDER STRUCTURES IN MG AND MG ALLOYS. [Internet] [Thesis]. Penn State University; 2013. [cited 2021 Jan 27].
Available from: https://submit-etda.libraries.psu.edu/catalog/19843.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Council of Science Editors:
Wang Y. A FIRST-PRINCIPLES STUDY OF STACKING FAULTS AND LONG PERIODIC STACKING ORDER STRUCTURES IN MG AND MG ALLOYS. [Thesis]. Penn State University; 2013. Available from: https://submit-etda.libraries.psu.edu/catalog/19843
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Penn State University
26.
Lee, Sung Hoon.
A STUDY OF IONIC MATERIALS FOR THE ENERGY APPLICATIONS THROUGH FIRST-PRINCIPLES CALCULATIONS AND CALPHAD MODELING.
Degree: 2011, Penn State University
URL: https://submit-etda.libraries.psu.edu/catalog/12059
► Computational thermodynamics have been steadily demonstrated to provide invaluable insight to identify materials exhibiting desirable properties. Especially, applications to the ionic materials as energy materials…
(more)
▼ Computational thermodynamics have been steadily demonstrated to provide invaluable insight to identify materials exhibiting desirable properties. Especially, applications to the ionic materials as energy materials are subject to great interest due to their importance in alternate energy source. In the present dissertation, three examples using CALPHAD (CALculation of PHAse Diagram) and first-principles calculations to aid materials design for energy applications are presented:
i) (La1-xCax)FeO3-δ perovskite is a potential candidate material for gas separation membrane. The defect chemistry and the energetics of (La1-xCax)FeO3-δ are studied owing to their importance in understanding its electrochemical performance. The interactions of multi-component and mul-tiple-defects are modeled using oxygen nonstoichiometry and the experimental phase equilibrium data. The calculated phase diagrams are in good agreement with experiments, and based on the models developed, the defect chemistry and the underlying energetics of (La1-xCax)FeO3-δ perovskite under various service conditions are predicted in terms of gas composition, pressure, temperature, and Ca content. The developed models hence provide guidance on operational pa-rameters of membranes, solid oxide fuel cells and other applications involving (La1-xCax)FeO3-δ perovskite.
i) LiBH4, owing to its high hydrogen density (18wt%), has been widely studied as a possible candidate for the hydrogen storage material. However, it desorbs hydrogen gas at a relatively high temperature (400 °C), and it is believed that strong ionic bonding is the main reason. Since the hydrogen atoms form covalent bond with boron atom, its effect is questionable, and as an effort to elucidate doping effect on the hydrogen desorption temperature, divalent metal-dopants,
Mg, Ca, and Zn, on the stability of LiBH4 is studied. Using the model parameters, their dehy-driding reactions are estimated in an effort to elucidate the energetically-preferred reaction me-chanism of metal with LiBH4.
iii) LiFePO4 is a promising electrode material for Li-ion battery. Phase transformation and elec-trochemical cell potential during insertion/deinsertion of Li+ ions are crucial properties which dictate the use of this material as an electrode. By using first-principles calculations, discharge voltage and enthalpy of formation are obtained, and phase diagram of the LiFePO4-FePO4 pseu-do-binary system and cell voltage change at a given condition are predicted by thermodynamic modeling.
Advisors/Committee Members: Dr Zi Kui Liu, Dissertation Advisor/Co-Advisor, Zi Kui Liu, Committee Chair/Co-Chair, Long Qing Chen, Committee Member, Clive A Randall, Committee Member, Jorge Osvaldo Sofo, Committee Member.
Subjects/Keywords: Ionic materials; energy; CALPHAD; first-principles
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APA (6th Edition):
Lee, S. H. (2011). A STUDY OF IONIC MATERIALS FOR THE ENERGY APPLICATIONS THROUGH FIRST-PRINCIPLES CALCULATIONS AND CALPHAD MODELING. (Thesis). Penn State University. Retrieved from https://submit-etda.libraries.psu.edu/catalog/12059
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Chicago Manual of Style (16th Edition):
Lee, Sung Hoon. “A STUDY OF IONIC MATERIALS FOR THE ENERGY APPLICATIONS THROUGH FIRST-PRINCIPLES CALCULATIONS AND CALPHAD MODELING.” 2011. Thesis, Penn State University. Accessed January 27, 2021.
https://submit-etda.libraries.psu.edu/catalog/12059.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
MLA Handbook (7th Edition):
Lee, Sung Hoon. “A STUDY OF IONIC MATERIALS FOR THE ENERGY APPLICATIONS THROUGH FIRST-PRINCIPLES CALCULATIONS AND CALPHAD MODELING.” 2011. Web. 27 Jan 2021.
Vancouver:
Lee SH. A STUDY OF IONIC MATERIALS FOR THE ENERGY APPLICATIONS THROUGH FIRST-PRINCIPLES CALCULATIONS AND CALPHAD MODELING. [Internet] [Thesis]. Penn State University; 2011. [cited 2021 Jan 27].
Available from: https://submit-etda.libraries.psu.edu/catalog/12059.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Council of Science Editors:
Lee SH. A STUDY OF IONIC MATERIALS FOR THE ENERGY APPLICATIONS THROUGH FIRST-PRINCIPLES CALCULATIONS AND CALPHAD MODELING. [Thesis]. Penn State University; 2011. Available from: https://submit-etda.libraries.psu.edu/catalog/12059
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Penn State University
27.
Mantina, Manjeera.
A FIRST-PRINCIPLES METHODOLOGY FOR
DIFFUSION COEFFICIENTS IN METALS AND DILUTE ALLOYS
.
Degree: 2008, Penn State University
URL: https://submit-etda.libraries.psu.edu/catalog/8681
► This work is a study exploring the extent of suitability of static first-principles calculations for studying diffusion in metallic systems. Specifically, vacancy-mediated volume diffusion in…
(more)
▼ This work is a study exploring the extent of suitability of static first-principles calculations for studying diffusion in metallic systems. Specifically, vacancy-mediated volume diffusion in pure elements and alloys with dilute concentration of impurities is studied.
A novel procedure is discovered for predicting diffusion coefficients that overcomes the shortcomings of the well-known transition
state theory, by Vineyard. The procedure that evolves from Eyring’s reaction rate theory yields accurate diffusivity results that include anharmonic effects within the quasi-harmonic approximation. Alongside, the procedure is straightforward in its application within the conventional harmonic approximation, from the results of static first-principles calculations.
To prove the extensibility of the procedure, diffusivities have been computed for a variety of systems. Over a wide temperature range, the calculated self-diffusion and impurity diffusion coefficients using local density approximation (LDA) of density functional theory (DFT) are seen to be in excellent match with experimental data. Self-diffusion coefficients have been calculated for: (i) fcc Al, Cu, Ni and Ag (ii) bcc W and Mo (v) hcp Mg, Ti and Zn. Impurity diffusion coefficients have been computed for: (i) Mg, Si, Cu, Li, Ag, Mo and 3d transition elements in fcc Al (ii) Mo, Ta in bcc W and Nb, Ta and W in bcc Mo (iii) Sn and Cd in hcp Mg and Al in hcp Ti. It is also an observation from this work, that LDA does not require surface correction for yielding energetics of vacancy-containing system in good comparison with experiments, unlike generalized gradient approximation (GGA).
It is known that first-principles’ energy minimization procedures based on electronic interactions are suited for metallic systems wherein the valence electrons are freely moving. In this thesis, research has been extended to study suitability of first-principles calculations within LDA / GGA including the localization parameter U, for Al system with transition metal solutes, in which charges are known to localize around the transition metal element. U parameter is determined from matching the diffusivities of 3d transition metal impurity in aluminum with reliable experimental data. The effort yielded activation energies in systematic agreement with experiments and has proved useful in obtaining insights into the complex interactions in these systems.
Besides the prediction of diffusion coefficients, this research has been helpful in understanding the physics underlying diffusion. Within the scope of observations from the systems studied, certain diffusion related aspects that have been clarified are: (i) cause for non-Arrnenius’ nature of diffusion plots (ii) definitions of atom migration properties (iii) magnitude and sign of diffusion parameters enthalpy and entropy of formation and migration and characteristic vibrational frequency (iv) trends in diffusivities based on activation energy and diffusion prefactor (vi) cause for anomalous diffusion behavior of 3d transition metals in…
Advisors/Committee Members: Zi Kui Liu, Committee Chair/Co-Chair, Long Qing Chen, Committee Chair/Co-Chair, Suzanne E Mohney, Committee Member, Jorge Osvaldo Sofo, Committee Member.
Subjects/Keywords: First-principles; tracer diffusion coefficients; metals; dilute alloys; fcc; bcc; hcp; self-diffusion; impurity diffusion
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APA ·
Chicago ·
MLA ·
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CSE |
Export
to Zotero / EndNote / Reference
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APA (6th Edition):
Mantina, M. (2008). A FIRST-PRINCIPLES METHODOLOGY FOR
DIFFUSION COEFFICIENTS IN METALS AND DILUTE ALLOYS
. (Thesis). Penn State University. Retrieved from https://submit-etda.libraries.psu.edu/catalog/8681
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Chicago Manual of Style (16th Edition):
Mantina, Manjeera. “A FIRST-PRINCIPLES METHODOLOGY FOR
DIFFUSION COEFFICIENTS IN METALS AND DILUTE ALLOYS
.” 2008. Thesis, Penn State University. Accessed January 27, 2021.
https://submit-etda.libraries.psu.edu/catalog/8681.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
MLA Handbook (7th Edition):
Mantina, Manjeera. “A FIRST-PRINCIPLES METHODOLOGY FOR
DIFFUSION COEFFICIENTS IN METALS AND DILUTE ALLOYS
.” 2008. Web. 27 Jan 2021.
Vancouver:
Mantina M. A FIRST-PRINCIPLES METHODOLOGY FOR
DIFFUSION COEFFICIENTS IN METALS AND DILUTE ALLOYS
. [Internet] [Thesis]. Penn State University; 2008. [cited 2021 Jan 27].
Available from: https://submit-etda.libraries.psu.edu/catalog/8681.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Council of Science Editors:
Mantina M. A FIRST-PRINCIPLES METHODOLOGY FOR
DIFFUSION COEFFICIENTS IN METALS AND DILUTE ALLOYS
. [Thesis]. Penn State University; 2008. Available from: https://submit-etda.libraries.psu.edu/catalog/8681
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Penn State University
28.
Schaut, Robert A.
The effect of boron oxide on the composition, structure, and adsorptivity of glass surfaces.
Degree: 2008, Penn State University
URL: https://submit-etda.libraries.psu.edu/catalog/8478
► Boron oxide has been added to commercial silicate glasses for many years to aid in lowering melting temperatures, lowering thermal expansion, and controlling chemical durability.…
(more)
▼ Boron oxide has been added to commercial silicate glasses for many years to aid in lowering melting temperatures, lowering thermal expansion, and controlling chemical durability. The fact that simple borate glasses have rather high thermal expansion and low chemical durability attests to the unique influence of boron oxide additions upon the properties of silicate glasses. However, the impact of boron oxide additions upon surface properties of multicomponent borosilicates such as adsorption and reactivity is not yet well understood. In particular, the presence of multiple coordination states for boron is expected to introduce adsorption sites with different acidic or basic behavior, but their existence is yet unproven. To investigate these effects, multicomponent sodium aluminosilicate glasses have been prepared with varying sodium and boron concentrations and drawn into moderately high-surface-area continuous filament fibers.
A relatively new technique, boron K-edge Near-Edge X-ray Absorption Fine Structure (NEXAFS) spectroscopy is applied to study the local boron coordination at fracture and melt-derived fiber surfaces of these glasses. This structural information is combined with surface compositional information by X-ray Photoelectron Spectroscopy (XPS) to characterize the local atomic structure of boron at the as-formed glass surface. Finally, this information is used to interpret the adsorptivity of these as-formed and leached surfaces toward short-chain alcohol molecules through a new Inverse Gas Chromatography - Temperature Programmed Desorption (IGC-TPD) experiment. The results clearly show that boron additions to alkali-free glass surfaces introduce a unique adsorption site which is not present on boron-free glass surfaces and is easily removed by leaching in acidic solutions.
Advisors/Committee Members: Carlo G Pantano, Committee Chair/Co-Chair, Jorge Osvaldo Sofo, Committee Member, Karl Todd Mueller, Committee Member, James Hansell Adair, Committee Member, Victor Alexandrovich Bakaev, Committee Member.
Subjects/Keywords: NEXAFS; XPS; TPD-IGC; Boron; Glass; Surfaces; XANES; coordination; adsorption; composition
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APA ·
Chicago ·
MLA ·
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CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Schaut, R. A. (2008). The effect of boron oxide on the composition, structure, and adsorptivity of glass surfaces. (Thesis). Penn State University. Retrieved from https://submit-etda.libraries.psu.edu/catalog/8478
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Chicago Manual of Style (16th Edition):
Schaut, Robert A. “The effect of boron oxide on the composition, structure, and adsorptivity of glass surfaces.” 2008. Thesis, Penn State University. Accessed January 27, 2021.
https://submit-etda.libraries.psu.edu/catalog/8478.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
MLA Handbook (7th Edition):
Schaut, Robert A. “The effect of boron oxide on the composition, structure, and adsorptivity of glass surfaces.” 2008. Web. 27 Jan 2021.
Vancouver:
Schaut RA. The effect of boron oxide on the composition, structure, and adsorptivity of glass surfaces. [Internet] [Thesis]. Penn State University; 2008. [cited 2021 Jan 27].
Available from: https://submit-etda.libraries.psu.edu/catalog/8478.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Council of Science Editors:
Schaut RA. The effect of boron oxide on the composition, structure, and adsorptivity of glass surfaces. [Thesis]. Penn State University; 2008. Available from: https://submit-etda.libraries.psu.edu/catalog/8478
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Penn State University
29.
Zhong, Yu.
Investigation in Mg-Al-Ca-Sr-Zn System by Computational Thermodynamics Approach Coupled with First-Principles Energetics and Experiments
.
Degree: 2008, Penn State University
URL: https://submit-etda.libraries.psu.edu/catalog/6088
► The thermodynamic database for the Mg-Al-Ca-Sr-Zn quinary system was constructed with the combined CALPHAD, first-principles calculations, and experiments approach. There are ten binary systems, six…
(more)
▼ The thermodynamic database for the Mg-Al-Ca-Sr-Zn quinary system was constructed with the combined CALPHAD, first-principles calculations, and experiments approach. There are ten binary systems, six of which were investigated in detail to develop their thermodynamic descriptions. There are ten ternary systems, in which Mg-Al-Ca ternary system was investigated. They were evaluated using Thermo-Calc, the software developed at The Royal Institute of Technology, Sweden.
The Ca-Sr system was modeled by using random solution models. Al-Mg binary system was remodeled with the help of the first-principles calculation results for g-Al12Mg17, e-Al30Mg23, and three laves phases at the Al2Mg composition. In modeling of the Al-Sr system, both random solution and associate models were applied to the liquid phase. It was also demonstrated for the Al-Sr system that the first-principles calculations provide reliable enthalpies of formation for stoichiometric compounds. Al3Sr8 phase is predicted and added into the Al-Sr system. The Ca-Mg system were modified with two-sublattice model (Mg,Ca)2(Mg,Ca) for the Mg2Ca laves-C14 phase. First-principles calculations provide reliable enthalpies of formation for non-stable end-members of the Mg2Ca phase. All compounds in the Mg-Sr binary system were calculated with first-principles calculations. The Mg-Sr thermodynamic database was constructed with the prediction that Mg38Sr9 may be not stable at low temperature. The Sr-Zn system was modeled using the random solution model for liquid.
The constructed quinary database was used to calculate the liquidus projections of the ternary systems, i.e. Mg-Al-Ca, Mg-Al-Sr, Mg-Al-Zn, Mg-Ca-Sr, Mg-Ca-Zn, Mg-Sr-Zn, Al-Ca-Sr, Al-Ca-Zn, Al-Sr-Zn, and Ca-Sr-Zn. Their primary crystallization fields, invariant reaction points, and possible ternary laves phases were predicted. First-principles calculations were performed for ternary laves phases in the Mg-Al-Ca system with the help from Special Quasirandom Structures (SQS’s). The existence of (Mg,Al)2Ca C36 phase is predicted by first-principles calculations and added into the Mg-Al-Ca database, which shows a good agreement with existing experimental data. The existence of the ternary Al2(Mg,Ca) phase predicted by first-principles calculations was verified by diffusion couples between pure Al and a Mg-Ca alloy.
The database was used to understand the creep resistance of Mg alloys at elevated temperatures by study phase stabilities through Scheil simulations and equilibrium calculations. The addition effect of Ca, Sr, and Zn on AM50 alloy is discussed and the available experimental observations in Mg-Al-Ca, Mg-Al-Sr, and Mg-Al-Zn alloys were successfully explained. The recent discovery of C36 phase in the as-cast samples of GM-C alloys was also explained. The combined effect of Ca, Sr, and Zn on AM50 alloy was predicted. The addition of Ca and Sr should be helpful to the creep resistance of Mg-Al-Zn alloys with the precipitation of Al2Ca-C15, C36, and Al4Sr.
Advisors/Committee Members: Vincent Henry Crespi, Committee Member, Jorge Osvaldo Sofo, Committee Member, Long Qing Chen, Committee Member, Zi Kui Liu, Committee Chair/Co-Chair.
Subjects/Keywords: Computational Thermodynamics; Mg Alloy; Creep Resistance; First-Principles
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APA ·
Chicago ·
MLA ·
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CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Zhong, Y. (2008). Investigation in Mg-Al-Ca-Sr-Zn System by Computational Thermodynamics Approach Coupled with First-Principles Energetics and Experiments
. (Thesis). Penn State University. Retrieved from https://submit-etda.libraries.psu.edu/catalog/6088
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Chicago Manual of Style (16th Edition):
Zhong, Yu. “Investigation in Mg-Al-Ca-Sr-Zn System by Computational Thermodynamics Approach Coupled with First-Principles Energetics and Experiments
.” 2008. Thesis, Penn State University. Accessed January 27, 2021.
https://submit-etda.libraries.psu.edu/catalog/6088.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
MLA Handbook (7th Edition):
Zhong, Yu. “Investigation in Mg-Al-Ca-Sr-Zn System by Computational Thermodynamics Approach Coupled with First-Principles Energetics and Experiments
.” 2008. Web. 27 Jan 2021.
Vancouver:
Zhong Y. Investigation in Mg-Al-Ca-Sr-Zn System by Computational Thermodynamics Approach Coupled with First-Principles Energetics and Experiments
. [Internet] [Thesis]. Penn State University; 2008. [cited 2021 Jan 27].
Available from: https://submit-etda.libraries.psu.edu/catalog/6088.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Council of Science Editors:
Zhong Y. Investigation in Mg-Al-Ca-Sr-Zn System by Computational Thermodynamics Approach Coupled with First-Principles Energetics and Experiments
. [Thesis]. Penn State University; 2008. Available from: https://submit-etda.libraries.psu.edu/catalog/6088
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Penn State University
30.
Wang, Tao.
AN INTEGRATED APPROACH FOR MICROSTRUCTURE SIMULATION: APPLICATION TO NI-AL-MO ALLOYS.
Degree: 2008, Penn State University
URL: https://submit-etda.libraries.psu.edu/catalog/7197
► The properties and performance of a material are strongly dependent on its microstructure. For example, the gamma' precipitate coherently embedded in the gamma matrix is…
(more)
▼ The properties and performance of a material are strongly dependent on its microstructure. For example, the gamma' precipitate coherently embedded in the gamma matrix is the primary strengthening phase in Ni-base superalloys, and its volume fraction, morphology and size distribution largely determine the strength, fatigue and creep properties of an alloy. In the present study, a multiscale computational approach was proposed to predict the microstructure evolution in Ni-base superalloys. It integrated a quantitative phase-field model with first-principles calculations as well as the CALPHAD (CALculation of PHAse Diagram) technique. Fundamental materials property databases such as lattice parameters and atomic mobility were developed.
A phenomenological model was developed to describe the lattice parameter in solid states as a function of temperature and composition, and successfully applied to Ni-Al binary system by evaluating the model parameters using experimental data. An integrated computational approach was also proposed for evaluating the lattice misfit between the matrix and precipitates by combining first-principles calculations, existing experimental data and phenomenological modeling when the experimental data is limited. The lattice parameters and the local lattice distortions around solute atoms in gamma-Ni solutions were studied using first-principles calculations. The solute atoms considered include Al, Co, Cr, Hf, Mo, Nb, Re, Ru, Ta, Ti and W. The effects of the atomic size and the electronic and magnetic interactions on lattice distortion have been discussed.
Atomic mobility in disordered gamma and ordered gamma' phases was modeled for the Ni-Al-Mo ternary system, and a kinetic database was developed. The diffusion of Al in gamma' was simulated, and the formation energies of vacancy in different sublattices were calculated by first-principles approach, both of which indicate the anti-site diffusion mechanism being dominant for diffusion of Al.
The phase-field model for binary Ni-base superalloys was extended to ternary systems and integrated with the corresponding thermodynamic, kinetic and lattice parameter databases. The microstructure evolutions and coarsening kinetics of gamma' precipitates in Ni-Al-Mo alloys were studied by two-dimensional phase-field simulations. The effects of volume fraction of precipitates and Mo concentration have been analyzed.
Advisors/Committee Members: Zi Kui Liu, Committee Chair/Co-Chair, Long Qing Chen, Committee Chair/Co-Chair, Padma Raghavan, Committee Member, Jorge Osvaldo Sofo, Committee Member.
Subjects/Keywords: Microstructure evolution; Ni-base superalloy; First-principle; CALPHAD; Phase-field
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❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Wang, T. (2008). AN INTEGRATED APPROACH FOR MICROSTRUCTURE SIMULATION: APPLICATION TO NI-AL-MO ALLOYS. (Thesis). Penn State University. Retrieved from https://submit-etda.libraries.psu.edu/catalog/7197
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Chicago Manual of Style (16th Edition):
Wang, Tao. “AN INTEGRATED APPROACH FOR MICROSTRUCTURE SIMULATION: APPLICATION TO NI-AL-MO ALLOYS.” 2008. Thesis, Penn State University. Accessed January 27, 2021.
https://submit-etda.libraries.psu.edu/catalog/7197.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
MLA Handbook (7th Edition):
Wang, Tao. “AN INTEGRATED APPROACH FOR MICROSTRUCTURE SIMULATION: APPLICATION TO NI-AL-MO ALLOYS.” 2008. Web. 27 Jan 2021.
Vancouver:
Wang T. AN INTEGRATED APPROACH FOR MICROSTRUCTURE SIMULATION: APPLICATION TO NI-AL-MO ALLOYS. [Internet] [Thesis]. Penn State University; 2008. [cited 2021 Jan 27].
Available from: https://submit-etda.libraries.psu.edu/catalog/7197.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Council of Science Editors:
Wang T. AN INTEGRATED APPROACH FOR MICROSTRUCTURE SIMULATION: APPLICATION TO NI-AL-MO ALLOYS. [Thesis]. Penn State University; 2008. Available from: https://submit-etda.libraries.psu.edu/catalog/7197
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
◁ [1] [2] ▶
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Open Access Theses and Dissertations