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You searched for subject:(VSEPR). Showing records 1 – 3 of 3 total matches.

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University of Texas – Austin

1. -6705-8755. From basis sets to force fields : improving methods for high-accuracy quantum chemical calculations of small molecules.

Degree: PhD, Chemistry, 2016, University of Texas – Austin

The first section of this work details a force field modeled on VSEPR theory. Previous studies¹ from Bartell et al. have validated the use of the following function to describe repulsion between outer atoms, X [subscript i], bonded to a shared center, A, in binary compounds of the form AX [subscript n]: V=K/r [superscript n above subscript ij]. Here, K and n are parameters and r [subscript ij] is the distance between repelled atoms. Bartell et al. fixed the bond distances A-X [subscript i] so that the atoms X [subscript i] are “points-on-a-sphere” around the central atom A. Our current work extends this POS force field to include flexibility in the bond distances A-X [subscript i]. The functional form for the energy of the bonds is that of the Morse oscillator: V [subscript m, sub-subscript i] = D [subscript e](1  – exp[  – α(r [subscript i]  – Re)])². Here, D [subscript e], α, and R [subscript e] are parameters of the force field and r [subscript i] is the distance between atoms A and X [subscript i]. This extended VSEPR force field is applied to PF₅. Parameters were optimized to minimize differences between the VSEPR and MP2/cc-pVTZ PF₅ diagonal quadratic force constants. Quadratic and cubic bending and stretching force constants are presented and compared between Morse-POS and MP2/cc-pVTZ methods. The second section of this dissertation focuses on the analytical transformation of force constants and molecular properties between isotopologues. Within the Born-Oppenheimer approximation, potential energy surfaces of isotopologues are identical. When beginning an exploration of a Born-Oppenheimer potential energy surface, a molecular geometry is chosen and the energy and derivatives are calculated. The most efficient choice of coordinates for these derivatives is normal coordinates, which are mass dependent. This thesis details the transformation of force constants, dipole moments, derivatives of dipole moments, rotational constants, and Coriolis constants from one isotopologue to another. Two alternative systems of coordinates for use in quantum chemical calculations are rectilinear and curvilinear internal coordinates. Rectilinear internal coordinates express the displacement of atoms in a molecule as changes in bond length, bond angle, and dihedral angle as linear combinations of Cartesian coordinates. Though other internal coordinates exist, the previously mentioned are the most commonly used. There are immediate problems with the general use of rectilinear internal coordinates. When one calculates the displacement in Cartesian coordinates needed to increase a bond angle, the bond angle does not scale linearly with the Cartesian coordinates. The following thesis provides the derivation of equations that allow for the analytical transformation from rectilinear to curvilinear coordinates of first through fourth derivatives of the energy. As shown here, these transformations may also be used in converting between the force fields of isotopologues. Additionally, the transformations used between force fields of… Advisors/Committee Members: Stanton, John (John F.) (advisor), Ellison, Barney (committee member), Anslyn, Eric (committee member), Makarov, Dmitrii (committee member), Henkelman, Graeme (committee member).

Subjects/Keywords: Ab initio; VSEPR; Phosphorus pentafluoride; Force field; Isotopomer; VPT2; Dihydroxycarbene

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APA (6th Edition):

-6705-8755. (2016). From basis sets to force fields : improving methods for high-accuracy quantum chemical calculations of small molecules. (Doctoral Dissertation). University of Texas – Austin. Retrieved from http://hdl.handle.net/2152/47232

Note: this citation may be lacking information needed for this citation format:
Author name may be incomplete

Chicago Manual of Style (16th Edition):

-6705-8755. “From basis sets to force fields : improving methods for high-accuracy quantum chemical calculations of small molecules.” 2016. Doctoral Dissertation, University of Texas – Austin. Accessed October 24, 2019. http://hdl.handle.net/2152/47232.

Note: this citation may be lacking information needed for this citation format:
Author name may be incomplete

MLA Handbook (7th Edition):

-6705-8755. “From basis sets to force fields : improving methods for high-accuracy quantum chemical calculations of small molecules.” 2016. Web. 24 Oct 2019.

Note: this citation may be lacking information needed for this citation format:
Author name may be incomplete

Vancouver:

-6705-8755. From basis sets to force fields : improving methods for high-accuracy quantum chemical calculations of small molecules. [Internet] [Doctoral dissertation]. University of Texas – Austin; 2016. [cited 2019 Oct 24]. Available from: http://hdl.handle.net/2152/47232.

Note: this citation may be lacking information needed for this citation format:
Author name may be incomplete

Council of Science Editors:

-6705-8755. From basis sets to force fields : improving methods for high-accuracy quantum chemical calculations of small molecules. [Doctoral Dissertation]. University of Texas – Austin; 2016. Available from: http://hdl.handle.net/2152/47232

Note: this citation may be lacking information needed for this citation format:
Author name may be incomplete


University of Victoria

2. Dean, Natalie L. Mass spectrometry, mechanisms, and molecular models - combining research in mass spectrometric reaction monitoring and chemical education.

Degree: Department of Chemistry, 2018, University of Victoria

This thesis combines work in the areas of mass spectrometric reaction monitoring and chemical education. In the first part of this thesis, real-time mechanistic analysis using electrospray ionization mass spectrometry is reported. In Chapter 1, an introduction to the mass spectrometric instrumentation and methodologies used in this research is provided. In Chapter 2, the real-time mechanistic analysis of the Hiyama cross-coupling reaction using electrospray ionization mass spectrometry is reported, in particular, the fluoride-mediated rearrangement of phenylfluorosilanes that was found to occur even before catalyst addition. Combining Ph3SiF with a fluoride ion source under typical Hiyama cross-coupling conditions causes rapid formation of the expected [Ph3SiF2]–; however, ESI-MS analysis reveals that phenyl-fluoride exchange occurs concomitantly, also producing substantial quantities of [PhnSiF5–n]– (n = 0-2). The exchange process is verified using 19F NMR spectroscopy. This observation may have implications for Hiyama reaction protocols, which use transmetallation from triaryldifluorosilicates as a key step in cross-coupling. Optimization of the methodology used for real-time analysis by ESI-MS to reduce observed contamination from leaching of rubber septa additives is also discussed. In the second part of this thesis, the development and application of two different approaches for generating molecular models for the teaching molecular geometry and VSEPR theory in first year chemistry is reported. Chapter 4 details a method for the application of handheld 3D printing pens for producing models from ABS plastic. In Chapter 5, the development of laser-cut acrylic model kits is detailed, as well as the design and results of a quantitative study aimed at assessing their effectiveness for improving representational competence and comprehension of molecular geometry. Advisors/Committee Members: McIndoe, J. Scott (supervisor).

Subjects/Keywords: Mass Spectrometry; Chemical Education; VSEPR; Hiyama Cross-Coupling; Fluorophenylsilane; Molecular Geometry

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APA (6th Edition):

Dean, N. L. (2018). Mass spectrometry, mechanisms, and molecular models - combining research in mass spectrometric reaction monitoring and chemical education. (Masters Thesis). University of Victoria. Retrieved from https://dspace.library.uvic.ca//handle/1828/9383

Chicago Manual of Style (16th Edition):

Dean, Natalie L. “Mass spectrometry, mechanisms, and molecular models - combining research in mass spectrometric reaction monitoring and chemical education.” 2018. Masters Thesis, University of Victoria. Accessed October 24, 2019. https://dspace.library.uvic.ca//handle/1828/9383.

MLA Handbook (7th Edition):

Dean, Natalie L. “Mass spectrometry, mechanisms, and molecular models - combining research in mass spectrometric reaction monitoring and chemical education.” 2018. Web. 24 Oct 2019.

Vancouver:

Dean NL. Mass spectrometry, mechanisms, and molecular models - combining research in mass spectrometric reaction monitoring and chemical education. [Internet] [Masters thesis]. University of Victoria; 2018. [cited 2019 Oct 24]. Available from: https://dspace.library.uvic.ca//handle/1828/9383.

Council of Science Editors:

Dean NL. Mass spectrometry, mechanisms, and molecular models - combining research in mass spectrometric reaction monitoring and chemical education. [Masters Thesis]. University of Victoria; 2018. Available from: https://dspace.library.uvic.ca//handle/1828/9383


Brno University of Technology

3. Hort, Pavel. Vizualizace molekul pomocí OpenGL .

Degree: 2011, Brno University of Technology

Tato práce se zabývá vlastnostmi atomů, které ovlivňují tvar molekul. Věnuje se pravidlům, na jejichž základě se molekuly tvoří. Uvádí několik základních vlastností a zákonitostí, které mají dopad na konečnou geometrii molekuly. Další část textu popisuje několik možností pro zobrazení molekuly a zabývá se způsoby reprezentace atomů a molekul v počítačové technice. Následující kapitoly uvádí možnosti řešení této problematiky a popisují řešení těchto problémů použité v této práci.; This thesis considers atom`s attributes, which affects shape of molecules. It describes rules that are basic for molecule creation. This text features basic attributes and rules, which affects the final shape of molecule. Next part of this text explains several ways to display molecule. Following parts of this thesis describes several ways how to store and represent atom and molecules in computer technology along with solution of these problems that are used for this thesis. Advisors/Committee Members: Kubíček, Radek (advisor).

Subjects/Keywords: chemie; atom; molekula; VSEPR; chemická vazba; vizualizace; tvorba molekul; 3D zobrazení molekul; sterické číslo; metoda AXE; OpenGL; CML; SMILES; SYBYL; Open Babel; chemistry; atom; molecule; VSEPR; chemical bond; visualization; creation of molecules; 3D representation of molecules; steric number; AXE method; OpenGL; CML; SMILES; SYBYL; Open Babel

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

APA (6th Edition):

Hort, P. (2011). Vizualizace molekul pomocí OpenGL . (Thesis). Brno University of Technology. Retrieved from http://hdl.handle.net/11012/54131

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):

Hort, Pavel. “Vizualizace molekul pomocí OpenGL .” 2011. Thesis, Brno University of Technology. Accessed October 24, 2019. http://hdl.handle.net/11012/54131.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7th Edition):

Hort, Pavel. “Vizualizace molekul pomocí OpenGL .” 2011. Web. 24 Oct 2019.

Vancouver:

Hort P. Vizualizace molekul pomocí OpenGL . [Internet] [Thesis]. Brno University of Technology; 2011. [cited 2019 Oct 24]. Available from: http://hdl.handle.net/11012/54131.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Hort P. Vizualizace molekul pomocí OpenGL . [Thesis]. Brno University of Technology; 2011. Available from: http://hdl.handle.net/11012/54131

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

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