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1. Hicks, Jason M. Computational Studies Of Oxides Relevant To Clean Energy, Catalytic Processing Of Renewables, And Biological Systems.

Degree: PhD, Chemistry, 2018, University of North Dakota

Computational chemistry has grown into a large field and is continuing to grow every year in both number and variety of applications. This dissertation will give a few such applications relevant to cleaner energy production from coal, catalytic degradation of renewable agricultural and forest waste into valuable chemicals, and extending the reach of electronic structure methods to systems of biological and macromolecular interest. The first two studies presented in this dissertation are concerned with the remediation of trace elements released into the environment through the combustion of coal for power production. In flue gases, arsenic and antimony exists most often as oxides. Despite the prevalence and importance of remediating these oxides, critical information on the thermodynamics of plausible intermediates and transition states in reaction pathways have been missing prior to these studies. Several of the intermediates, and essentially all transition states, were found to be electronically multiconfigurational for the arsenic oxides. In this work, the electronic structures of several oxides of arsenic, AsxOy, where x = 1, 2 and y = 1-5, were investigated using the second-order generalized van Vleck variant of multireference perturbation theory (GVVPT2), using the cc-pVTZ basis set, with comparison to multi-reference configuration interaction (MRCISD) and the linked completely renormalized coupled cluster through perturbative triple excitations (CR-CCSD(T)L or CR-CC(2,3)) when relevant. Calculated oxidation reaction energies for the formation of AsO2 and AsO3 from AsO were predicted to be energetically favorable and formation energies of the lowest energy compounds containing two metalloid atoms, called dimers for brevity, from the monomers were also predicted to be energetically favorable. The energetics of the monomers, five isomers of As2O3 and eleven isomers of As2O5 were characterized using a composite methodology along with the key transition states between the isomers. Geometry optimizations as well as harmonic vibrational frequencies of AsxOy were obtained at the B3LYP/6-311G* level of theory and gave satisfactory agreement with experimental data when available. It was discovered that several isomers of As2O3 and As2O5 have comparable energies and relatively low barrier heights. Therefore, we expect these isomers to be chemically relevant. The antimony oxides were also found to be electronically multiconfigurational. The electronic structures of several antimony oxides, SbxOy, where x = 1, 2 and y = 1-5, were investigated using GVVPT2 and the SBD-aug-cc-pVTZ basis set. The oxidation reaction energies of elemental antimony toward the formation of SbO and SbO2 was found to be energetically favorable, while the further oxidation of those species to SbO3 was found to be unfavorable. It was found that the accretion of the monomers into Sb2O3 was highly energetically favorable at both the B3LYP/SBD-aug-cc-pVTZ and GVVPT2/SBD-aug-cc-pVTZ//B3LYP/SBD-aug-cc-pVTZ levels of theory. However,… Advisors/Committee Members: Mark R. Hoffmann.

Subjects/Keywords: Cu2O2; electronic structure theory; GVVPT2; lignin; metalloid oxides; multireference perturbation theory

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APA (6th Edition):

Hicks, J. M. (2018). Computational Studies Of Oxides Relevant To Clean Energy, Catalytic Processing Of Renewables, And Biological Systems. (Doctoral Dissertation). University of North Dakota. Retrieved from https://commons.und.edu/theses/2232

Chicago Manual of Style (16th Edition):

Hicks, Jason M. “Computational Studies Of Oxides Relevant To Clean Energy, Catalytic Processing Of Renewables, And Biological Systems.” 2018. Doctoral Dissertation, University of North Dakota. Accessed March 06, 2021. https://commons.und.edu/theses/2232.

MLA Handbook (7th Edition):

Hicks, Jason M. “Computational Studies Of Oxides Relevant To Clean Energy, Catalytic Processing Of Renewables, And Biological Systems.” 2018. Web. 06 Mar 2021.

Vancouver:

Hicks JM. Computational Studies Of Oxides Relevant To Clean Energy, Catalytic Processing Of Renewables, And Biological Systems. [Internet] [Doctoral dissertation]. University of North Dakota; 2018. [cited 2021 Mar 06]. Available from: https://commons.und.edu/theses/2232.

Council of Science Editors:

Hicks JM. Computational Studies Of Oxides Relevant To Clean Energy, Catalytic Processing Of Renewables, And Biological Systems. [Doctoral Dissertation]. University of North Dakota; 2018. Available from: https://commons.und.edu/theses/2232

2. Li, Run. Theory And Application Development Of Electronic Structure Methods Involving Heavy Computation.

Degree: PhD, Chemistry, 2017, University of North Dakota

The propargyl radical, the most stable isomer of C3H3, is very important in combustion reactions. However, theoretical calculations have never been able to find a strong absorption around 242 nm as seen in experiments. In this study, we calculated the electronic energy levels of the propargyl radical using highly accurate multireference methods, including multireference configuration interaction singles and doubles method with triples and quadruples treated perturbatively [denoted as MRCISD(TQ)], as well as second and third order generalized Van Vleck perturbation theories (GVVPT2 and GVVPT3). Calculations indicate that this absorption can be solely attributed to a Franck-Condon-allowed transition from the ground B1 state to the Rydberg-like first A1 excited state. Calculations also show that GVVPT2 with a relatively small active space fails to capture enough Rydberg character of this excited state, while it can be recovered by GVVPT3, MRCISD, and MRCISD(TQ). In order to speed up MRCISD(TQ) calculations, the triple and quadruple (TQ) perturbative corrections, the most time-consuming part of MRCISD(TQ) calculations, were parallelized using Message Passing Interface (MPI). The MRCISD(TQ) method is organized in the framework of macroconfigurations, which allows the use of incomplete reference spaces and provides an efficient means of screening large number of non-interacting configuration state functions (CSFs). The test calculations show that the parallel code achieved close to linear speed-up when the number of CSFs in each macroconfiguration is small. The speed-up suffers when large numbers of CSFs exist in only a few macroconfigurations. The computer algorithm for second-order generalized van Vleck multireference perturbation theory (GVVPT2) was similarly parallelized using the MPI protocol, organized in the framework of macroconfigurations. The maximum number of CSFs per macroconfiguration is found to have less influence on the MPI speedup and scaling than in the case of MRCISD(TQ). It was previously found that unrestricted local density approximation (LDA) orbitals can be used in place of MCSCF to provide orbitals for GVVPT2. This inspired us to use the more controllable restricted density functional theory (DFT) to provide unbiased orbitals for GVVPT2 calculations. In this study, the relationship between restricted DFT and unrestricted DFT were explored and the restricted DFT results were obtained by utilizing subroutines from unrestricted DFT calculations. We also found that the DIIS technique drastically sped up the convergence of RDFT calculations. Plane wave DFT methods are commonly used to efficiently evaluate solid state materials. In this work, the electronic properties of pristine graphene and Zn-phthalocyanine tetrasulfonic acid (Zn-PcS) physisorbed on single-layer graphene were calculated using plane wave DFT. The Perdew-Burke-Ernzerhof functional with dispersion correction (PBE-D2) was used. The densities of states were… Advisors/Committee Members: Mark R. Hoffmann.

Subjects/Keywords: electronic structure theory; GVVPT2; MPI; MRCISD(TQ); multireference perturbation theory; parallelization

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Li, R. (2017). Theory And Application Development Of Electronic Structure Methods Involving Heavy Computation. (Doctoral Dissertation). University of North Dakota. Retrieved from https://commons.und.edu/theses/2269

Chicago Manual of Style (16th Edition):

Li, Run. “Theory And Application Development Of Electronic Structure Methods Involving Heavy Computation.” 2017. Doctoral Dissertation, University of North Dakota. Accessed March 06, 2021. https://commons.und.edu/theses/2269.

MLA Handbook (7th Edition):

Li, Run. “Theory And Application Development Of Electronic Structure Methods Involving Heavy Computation.” 2017. Web. 06 Mar 2021.

Vancouver:

Li R. Theory And Application Development Of Electronic Structure Methods Involving Heavy Computation. [Internet] [Doctoral dissertation]. University of North Dakota; 2017. [cited 2021 Mar 06]. Available from: https://commons.und.edu/theses/2269.

Council of Science Editors:

Li R. Theory And Application Development Of Electronic Structure Methods Involving Heavy Computation. [Doctoral Dissertation]. University of North Dakota; 2017. Available from: https://commons.und.edu/theses/2269

3. Hicks, Jason. Theoretical Studies Of Oxides Relevant To The Combustion Of Fossil Fuels.

Degree: MS, Chemistry, 2013, University of North Dakota

Anthropogenic pollution has greatly increased since the industrial revolution and continues to increase as more of the world becomes dependent upon fossil fuels for important applications like transportation and power production. In a general case, whenever a fossil fuel is consumed, a primary product of a complete combustion reaction is carbon dioxide. In a more specific case, the collection, processing and combustion of coal for power production are one of the primary ways by which trace elements, such as arsenic and selenium, are released into the environment. All of these pollutants are known to have harmful effects, whether on the environment, human health or power production itself. Because of this there has been an increasing interest in studies related to combating these pollutants. Concerning CO2 emissions, recently there has been a significant amount of work related to CO2 capture. A promising method involves the encapsulation of CO2 into isoreticular metal-organic frameworks (IRMOFs). The effectiveness of IMROFs greatly depends on the choice of both metal and organic parts. Molecular simulations have been used in the past to aid in the design and characterization of new MOFs, in particular by generating an adsorption isotherm. However, these traditional simulation methods have several drawbacks. The method used in this thesis, namely expanded Wang-Landau, not only overcomes these drawbacks but provides access to all the thermodynamic properties relevant to the adsorption process through a solution thermodynamics approach. This is greatly beneficial, since an excellent way to characterize the performance of various MOFs is by comparing their desorption free energy, i.e., the energy it takes to regenerate a saturated MOF to prepare it for the next adsorption cycle. Expanded WL was used in the study of CO2 adsorption into IRMOF-1, 8 and 10 at eight temperatures, spanning both the subcritical and supercritical regimes and the following were obtained: adsorption isotherms, Gibbs free energy, enthalpy, entropy and desorption free energy. It was found that, when the maximum loading was compared to the regeneration costs, IRMOF-10 had the best performance, followed by IRMOF-8 then IRMOF-1. During the combustion of coal, not only is CO2 produced, but also the trace elements of arsenic and selenium escape into the environment though this process. Both arsenic and selenium are known to have a harmful effects on the environment and human health. Arsenic is also known to poison the catalytic converter used in selective catalytic reduction of NOx. These trace elements have been found on fly ash or in the hot flue gases released into the atmosphere. In flue gases they most often exist as oxides. There have been many experimental and a few theoretical studies on the monomeric oxides, AsOx and SeOx, where x = 1, 2, or 3. However, little is known concerning the corresponding… Advisors/Committee Members: Jerome Delhommelle, Mark R. Hoffmann.

Subjects/Keywords: arsenic oxide; carbon dioxide; Expanded Wang-Landau; GVVPT2; IRMOF; selenium oxide

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Hicks, J. (2013). Theoretical Studies Of Oxides Relevant To The Combustion Of Fossil Fuels. (Masters Thesis). University of North Dakota. Retrieved from https://commons.und.edu/theses/1544

Chicago Manual of Style (16th Edition):

Hicks, Jason. “Theoretical Studies Of Oxides Relevant To The Combustion Of Fossil Fuels.” 2013. Masters Thesis, University of North Dakota. Accessed March 06, 2021. https://commons.und.edu/theses/1544.

MLA Handbook (7th Edition):

Hicks, Jason. “Theoretical Studies Of Oxides Relevant To The Combustion Of Fossil Fuels.” 2013. Web. 06 Mar 2021.

Vancouver:

Hicks J. Theoretical Studies Of Oxides Relevant To The Combustion Of Fossil Fuels. [Internet] [Masters thesis]. University of North Dakota; 2013. [cited 2021 Mar 06]. Available from: https://commons.und.edu/theses/1544.

Council of Science Editors:

Hicks J. Theoretical Studies Of Oxides Relevant To The Combustion Of Fossil Fuels. [Masters Thesis]. University of North Dakota; 2013. Available from: https://commons.und.edu/theses/1544

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