Law Chi-Kin. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2002. / Includes bibliographical references. / Abstracts in English and Chinese. / Abstract --- p.i / Acknowledgements --- p.iii / Table of Contents --- p.iv / List of Tables --- p.vi / List of Figures --- p.viii / Chapter Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- The Gaussian´ؤ3 Method --- p.1 / Chapter 1.2 --- The G3 Method with Reduced Mφller-Plesset Order and Basis Set --- p.2 / Chapter 1.3 --- The Gaussian-3X Method --- p.2 / Chapter 1.4 --- Calculation of Thermodynamical Data --- p.3 / Chapter 1.5 --- Remark on the Location of Equilibrium and Transition Structures --- p.3 / Chapter 1.6 --- Natural Bond Orbital (NBO) Analysis --- p.4 / Chapter 1.7 --- Scope of the Thesis --- p.4 / Chapter 1.8 --- References --- p.5 / Chapter Chapter 2 --- Gaussian´ؤ3 Heats of Formation for (CH)6 Isomers --- p.6 / Chapter 2.1 --- Introduction --- p.6 / Chapter 2.2 --- Methods of Calculation and Results --- p.7 / Chapter 2.3 --- Discussion --- p.9 / Chapter 2.4 --- Conclusion --- p.11 / Chapter 2.5 --- Publication Note --- p.12 / Chapter 2.6 --- References --- p.12 / Chapter Chapter 3 --- A Gaussian-3 Investigation of N7 Isomers --- p.14 / Chapter 3.1 --- Introduction --- p.14 / Chapter 3.2 --- Computational Method and Results --- p.16 / Chapter 3.3 --- Discussion --- p.16 / Chapter 3.4 --- Conclusion --- p.24 / Chapter 3.5 --- Publication Note --- p.24 / Chapter 3.6 --- References --- p.24 / Chapter Chapter 4 --- A Gaussian-3 Study of N7+ and N7- Isomers --- p.27 / Chapter 4.1 --- Introduction --- p.27 / Chapter 4.2 --- Computational Method and Results --- p.29 / Chapter 4.3 --- Discussion --- p.30 / Chapter 4.3.1 --- The N7+ isomers --- p.30 / Chapter 4.3.2 --- The N7- isomers --- p.37 / Chapter 4.4 --- Conclusion --- p.41 / Chapter 4.5 --- Publication Note --- p.41 / Chapter 4.6 --- References --- p.41 / Chapter Chapter 5 --- "Thermochemistry of Chlorine Fluorides ClFn, n = 1-7, and Their Singly Charged Cations and Anions: A Gaussian-3 and Gaussian-3X Study" --- p.45 / Chapter 5.1 --- Introduction --- p.45 / Chapter 5.2 --- Methods of Calculations --- p.47 / Chapter 5.3 --- Results and Discussion --- p.48 / Chapter 5.3.1 --- Comparison of the G3 and G3X methods --- p.48 / Chapter 5.3.2 --- Assessments of the experimental results --- p.54 / Chapter 5.3.3 --- "Bond dissociation energies of ClFn, ClFn+, and ClFn-" --- p.57 / Chapter 5.3.4 --- Summary of the thermochemical data --- p.58 / Chapter 5.4 --- Conclusion --- p.59 / Chapter 5.5 --- Publication Note --- p.60 / Chapter 5.6 --- References --- p.60 / Chapter Chapter 6 --- A Gaussian-3 Study of the Photoionization and Dissociative Photoionization Channels of Dimethyl Sulfide --- p.63 / Chapter 6.1 --- Introduction --- p.63 / Chapter 6.2 --- Methods of Calculations --- p.64 / Chapter 6.3 --- Results and Discussion --- p.64 / Chapter 6.3.1 --- Bond cleavage reactions --- p.67 / Chapter 6.3.2 --- Dissociation channels involving transition structures --- p.68 / Chapter 6.4 --- Conclusion --- p.70 / Chapter 6.5 --- Publication Note --- p.70 / Chapter 6.6 --- References --- p.70 / Chapter Chapter 7 --- "Theoretical Study of the Electronic Structures of Carbon and Silicon Nanotubes, Carbon and Silicon Nanowires" --- p.72 / Chapter 7.1 --- Introduction --- p.72 / Chapter 7.2 --- Models and Computational Methods --- p.74 / Chapter 7.3 --- Results and Discussion --- p.75 / Chapter 7.4 --- Conclusion --- p.87 / Chapter 7.5 --- Publication Note --- p.87 / Chapter 7.6 --- References --- p.87 / Chapter Chapter 8 --- Conclusion --- p.90 / Appendix A --- p.91 / Appendix B

Cheng Mei-Fun. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2003. / Includes bibliographical references. / Abstracts in English and Chinese. / Abstract --- p.i / Acknowledgements --- p.iii / Table of Contents --- p.iv / List of Tables --- p.vi / List of Figures --- p.viii / Chapter Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- The Gaussian-3 Method --- p.1 / Chapter 1.2 --- The G3 Method with Reduced Mφller-Plesset Order and Basis Set --- p.2 / Chapter 1.3 --- Density Functional Theory (DFT) --- p.3 / Chapter 1.4 --- Calculation of Thermodynamical Data --- p.3 / Chapter 1.5 --- Remark on the Location of Transition Structures --- p.3 / Chapter 1.6 --- Natural Bond Orbital (NBO) Analysis --- p.4 / Chapter 1.7 --- Scope of the Thesis --- p.4 / Chapter 1.8 --- References --- p.5 / Chapter Chapter 2 --- Heats of Formation for the Azine Series: A Gaussian-3 Study --- p.7 / Chapter 2.1 --- Introduction --- p.7 / Chapter 2.2 --- Methods of Calculation and Results --- p.8 / Chapter 2.3 --- Discussion --- p.8 / Chapter 2.4 --- Conclusion --- p.9 / Chapter 2.5 --- Publication Note --- p.10 / Chapter 2.6 --- References --- p.10 / Chapter Chapter 3 --- Heats of Formation for Some Boron Hydrides: A Gaussian-3 Study --- p.16 / Chapter 3.1 --- Introduction --- p.16 / Chapter 3.2 --- Methods of Calculation and Results --- p.18 / Chapter 3.3 --- Discussion --- p.19 / Chapter 3.4 --- Conclusion --- p.21 / Chapter 3.5 --- Publication Note --- p.21 / Chapter 3.6 --- References --- p.21 / Chapter Chapter 4 --- Structural and Energetics Studies of Tri- and Tetra-tert-butylmethane --- p.30 / Chapter 4.1 --- Introduction --- p.30 / Chapter 4.2 --- Methods of Calculation and Results --- p.32 / Chapter 4.3 --- Discussion --- p.34 / Chapter 4.3.1 --- Mono-tert-butylmethane --- p.34 / Chapter 4.3.2 --- Di-tert-butylmethane --- p.35 / Chapter 4.3.3 --- Tri-tert-butylmethane --- p.37 / Chapter 4.3.4 --- Tetra-tert-butylmethane --- p.38 / Chapter 4.4 --- Conclusion --- p.39 / Chapter 4.5 --- Publication Note --- p.40 / Chapter 4.6 --- References --- p.40 / Chapter Chapter 5 --- A Computational Study of the Diels-Alder Reactions Involving Acenes: Reactivity and Aromaticity --- p.49 / Chapter 5.1 --- Introduction --- p.49 / Chapter 5.2 --- Methods of Calculation and Results --- p.50 / Chapter 5.3 --- Discussion --- p.51 / Chapter 5.4 --- Conclusion --- p.53 / Chapter 5.5 --- Publication Note --- p.53 / Chapter 5.6 --- References --- p.53 / Chapter Chapter 6 --- A Computational Study of the Charge- Delocalized and Charge-Localized Forms of the Croconate and Rhodizonate Dianions --- p.65 / Chapter 6.1 --- Introduction --- p.65 / Chapter 6.2 --- Methods of Calculation and Results --- p.67 / Chapter 6.3 --- Discussion --- p.68 / Chapter 6.3.1 --- Charge-Localized Forms of C5052- (C2v) and C6O6 2-(C2v) --- p.68 / Chapter 6.3.2 --- Charge-Delocalized Forms of C5052- (D5h) and C6062- (D6h) --- p.71 / Chapter 6.4 --- Conclusion --- p.72 / Chapter 6.5 --- Publication Note --- p.73 / Chapter 6.6 --- References --- p.74 / Chapter Chapter 7 --- Conclusion --- p.89 / Appendix A --- p.90 / Appendix B --- p.92

Lau Kai-Chi. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2001. / Includes bibliographical references. / Abstracts in English and Chinese. / Abstract --- p.i / Acknowledgements --- p.iii / Table of Contents --- p.iv / Chapter Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- The Gaussian´ؤ3 Method --- p.1 / Chapter 1.2 --- The G3 Method with Reduced MΦ ller-Plesset Order and Basis Set --- p.2 / Chapter 1.3 --- The Gaussian-3X Method --- p.2 / Chapter 1.4 --- The Modified G2 Method --- p.3 / Chapter 1.5 --- Calculation of Thermodynamical Data --- p.3 / Chapter 1.6 --- Remark on the Location of Transition Structures --- p.4 / Chapter 1.7 --- Scope of the Thesis --- p.4 / Chapter 1.8 --- References --- p.4 / Chapter Chapter 2 --- "A Gaussian-2 and Gaussian-3 Study of Alkoxide Anion Decompositions. I. H2 and CH4 Eliminations of the Methoxide, Ethoxide, i-Propoxide, and t-Butoxide Anions" --- p.6 / Chapter 2.1 --- Introduction --- p.6 / Chapter 2.2 --- Methods of Calcuations --- p.7 / Chapter 2.3 --- Results and Discussion --- p.8 / Chapter 2.3.1 --- Nature of ion-neutral complex --- p.8 / Chapter 2.3.2 --- Initial bond cleavage of alkoxide anions --- p.9 / Chapter 2.3.3 --- Dissociation of alkoxide anions --- p.10 / Chapter 2.4 --- Conclusions --- p.23 / Chapter 2.5 --- Publication Note --- p.25 / Chapter 2.6 --- References --- p.25 / Chapter Chapter 3 --- A Gaussian-2 and Gaussian-3 Study of Alkoxide Anion Decompositions. II. Alkane Eliminations of (CH3)2(C2H5)CO- and (i-Pr)(C2H5)2CO- --- p.28 / Chapter 3.1 --- Introduction --- p.28 / Chapter 3.2 --- Methods of Calculations --- p.29 / Chapter 3.3 --- Results and Discussion --- p.29 / Chapter 3.3.1 --- Initial bond cleavage of alkoxide anions --- p.30 / Chapter 3.3.2 --- Dissociation of alkoxde anions --- p.31 / Chapter 3.3.3 --- General dissociation mechanism of alkoxide anions --- p.35 / Chapter 3.4 --- Conclusions --- p.37 / Chapter 3.5 --- References --- p.37 / Chapter Chapter 4 --- A Gaussian-3 Study of the Photoionization and Dissociative Photoionization Channels of Dimethyl Disulfide --- p.40 / Chapter 4.1 --- Introduction --- p.40 / Chapter 4.2 --- Methods of Calculations --- p.41 / Chapter 4.3 --- Results and Discussion --- p.41 / Chapter 4.3.1 --- Bond cleavage reactions --- p.44 / Chapter 4.3.2 --- Dissociation channels involving transition structures --- p.45 / Chapter 4.4 --- Conclusions --- p.48 / Chapter 4.5 --- References --- p.48 / Chapter Chapter 5 --- A Gaussian´ؤ3 Study of the Photodissociation Channels of Propylene Sulfide --- p.50 / Chapter 5.1 --- Introduction --- p.50 / Chapter 5.2 --- Methods of Calculations --- p.51 / Chapter 5.3 --- Results and Discussion --- p.51 / Chapter 5.3.1 --- The dissociation channels involving transition structures --- p.53 / Chapter 5.3.2 --- The dissociations of sulfur atom --- p.56 / Chapter 5.4 --- Conclusions --- p.58 / Chapter 5.5 --- References --- p.59 / Chapter Chapter 6 --- Thermochemistry of Phosphorus Fluorides: A Gaussian´ؤ3 and Gaussian´ؤ3X Study --- p.60 / Chapter 6.1 --- Introduction --- p.60 / Chapter 6.2 --- Methods of Calculations --- p.62 / Chapter 6.3 --- Results and Discussion --- p.62 / Chapter 6.3.1 --- Comparison of the G3 and G3X methods --- p.62 / Chapter 6.3.2 --- Assessments of the experimental results --- p.65 / Chapter 6.4 --- Conclusions --- p.71 / Chapter 6.5 --- References --- p.71 / Chapter Chapter 7 --- Conclusions --- p.74 / Appendix A --- p.75 / Appendix B --- p.78

Magnetic resonance imaging (MRI) and magnetic resonance spectroscopy (MRS) has been developed and applied to clinical analysis studies due to its non-invasive properties. Because of the increasing clinical interests of applying MRS, a lot of post-processing tools has been developed, among which LCModel is one of the most popular. LCModel estimates the absolute metabolite concentrations in vivo according to the basis file, so basis files play an important role for the accuracy of absolute metabolite concentrations. The default basis sets of LCModel were made by phantom experiments. However, some special metabolites are difficult to get them, so the basis sets lack for these metabolites. In order to avoid this trouble, LCModel provides a special method called ¡§spectra offering¡¨. In this study, we use GAMMA Visual Analysis (GAVA) software to create basis sets and compare the shape of LCModel default basis sets with the shape of GAVA basis sets. Some metabolites which are not included in the LCModel phantom experiments are also generated. Finally, we estimate the absolute concentrations in normal subjects and patients by using these two kinds of basis sets respectively. Using LCModel ¡§spectra offering¡¨ method to append extra metabolites for LCModel basis sets is applicable to those metabolites of singlet resonance but not of J-coupling resonance in the meanwhile. Our results demonstrate that using GAVA simulation as the basis set leads to different quantitative results from using basis sets of in vitro. We believe that using GAVA simulation as the basis set would provide better consistency among all metabolites and thus achieve more accurate quantification of MRS.

Thesis (Ph. D.)--University of North Texas, May, 2009. / Title from title page display. Includes bibliographical references.

Thesis (Ph. D.)--Ohio State University, 2005. / Title from second page of PDF file. Document formatted into pages; contains xxiii, 151 p.; also includes graphics (some col.). Includes bibliographical references (p. 140-151). Available online via OhioLINK's ETD Center

Estudos pioneiros na década de 1970 com cálculos ab initio inauguraram o campo da química quântica relativística computacional. Desde então, também devido ao crescimento exponencial da capacidade computacional, a aplicação de Hamiltonianos relativísticos em cálculos de química teórica tem se tornado cada vez mais frequente. No entanto, o desenvolvimento de conjuntos de funções de base para estes cálculos não seguiu no mesmo ritmo. Após décadas, as melhores opções disponíveis ainda apresentam certas limitações técnicas, como sinais de prolapso variacional. Desta forma, o objetivo deste trabalho foi a geração de eficientes conjuntos relativísticos de funções de base Gaussianas para aplicação em cálculos ab initio correlacionados. Usou-se então de uma versão polinomial do método da coordenada geradora Dirac-Fock para elaboração de um conjunto primitivo de funções otimizadas variacionalmente livres de prolapso. Funções de correlação/polarização e funções difusas foram adicionadas em acordo com uma incrementação do tipo quadruple-ζ. Estas funções foram escolhidas através do tratamento multi-referencial de interação de configurações com o Hamiltoniano Dirac-Coulomb. Cálculos moleculares de propriedades fundamentais atestaram a qualidade destes conjuntos, denominados RPF-4Z, em comparação com outras bases relativísticas bastante utilizadas na literatura. Adicionalmente, momentos de quadrupolo nuclear de isótopos de bismuto e potássio e uma curva de energia potencial do dímero de rádio foram obtidos com estes conjuntos. Ao prover funções de base que retornam resultados comparáveis a outros conjuntos relativísticos disponíveis de qualidade quadruple-ζ, mas com uma significativa redução na demanda computacional, espera-se que as bases RPF-4Z se traduzam em um grande avanço na área. / Pioneering studies with ab initio calculations from the 1970s gave rise to the computational relativistic quantum chemistry field. Since then, also due to the exponential growth in computational resources, the application of relativistic Hamiltonians in theoretical chemistry calculations has become more common. However, the development of basis sets to be used in such calculations have presented its struggles. After decades, technical limitations, such as the variational prolapse issue still persist. Hence, the aim of the present thesis was the development of efficient relativistic Gaussian basis sets to be applied in correlated ab initio calculations. In order to do that, a polynomial version of the generator coordinate Dirac-Fock method has been applied to obtain variationally optimized primitive sets that are free of prolapse. Correlating/polarization functions, as well as diffuse ones, were added to these sets in a quadruple-ζ type of increment. Such functions were chosen by means of the Dirac-Coulomb multi-reference configuration interaction treatment. Molecular calculations of fundamental properties have attested the high quality of the designated RPF-4Z sets in comparison with other well-known relativistic sets. Furthermore, nuclear electric quadrupole moments of bismuth and potassium isotopes and a potential energy curve of the radium dimer were also analyzed. Since these generated sets are as accurate as commonly used relativistic quadruple-ζ sets already available, but with the advantage of a reduced computational demand, the RPF-4Z sets are expected to represent a great advance in the field.

The development of the semi-empirical atomistic potential called the embedded atom method (EAM) has allowed for the efficient modeling of solid-state environments, at a lower computational cost than afforded by density functional theory (DFT). This offers the capability of EAM to model the energetics of solid-state phases of varying coordination, including defects, such as vacancies and self-interstitials. This dissertation highlights the development and application of two EAMs: a Ti potential constructed with the multi-state modified embedded atom method (MS-MEAM), and a Ni potential constructed with the fragment Hamiltonian (FH) method. Both potentials exhibit flexibility in the description of different solid-states phases and applications. This dissertation also outlines two applications of DFT. First, a study of structure and stability for solid-state forms of NixCy (in which x and y are integers) is investigated using plane-wave DFT. A ground state phase for Ni2C is elucidated and compared to known and hypothesized forms of NixCy. Also, a set of correlation consistent basis sets, previously constructed using the B3LYP and BLYP density functionals, are studied. They are compared to the well-known to the correlation consistent basis sets that were constructed with higher-level ab initio methodologies through computations of enthalpies of formation and combustion enthalpies. The computational accuracy with regard to experiment is reported.

The development of the correlation consistent basis sets, cc-pVnZ (where n = D, T, Q, etc.) have allowed for the systematic elucidation of the intrinsic accuracy of ab initio quantum chemical methods. In density functional theory (DFT), where the cc-pVnZ basis sets are not necessarily optimal in their current form, the elucidation of the intrinsic accuracy of DFT methods cannot always be accomplished. This dissertation outlines investigations into the basis set requirements for DFT and how the intrinsic accuracy of DFT methods may be determined with a prescription involving recontraction of the cc-pVnZ basis sets for specific density functionals. Next, the development and benchmarks of a set of cc-pVnZ basis sets designed for the s-block atoms lithium, beryllium, sodium, and magnesium are presented. Computed atomic and molecular properties agree well with reliable experimental data, demonstrating the accuracy of these new s-block basis sets. In addition to the development of cc-pVnZ basis sets, the development of a new, efficient formulism of the correlation consistent Composite Approach (ccCA) using the resolution of the identity (RI) approximation is employed. The new formulism, denoted 'RI-ccCA,' has marked efficiency in terms of computational time and storage, compared with the ccCA formulism, without the introduction of significant error. Finally, this dissertation reports three separate investigations of the properties of FOOF-like, germanium arsenide, and silicon hydride/halide molecules using high accuracy ab initio methods and the cc-pVnZ basis sets.

O método da Coordenada Geradora é uma poderosa ferramenta para gerar funções de base. Sua última versão, chamada de método da Coordenada Geradora polinomial, permite a geração de funções de base mais eficientes e precisas a um baixo custo computacional. Nesta tese, além da geração de funções de base para os átomos do primeiro período da Tabela Periódica, uma estratégia de selecionar expoentes da própria função de base para posteriormente refiná-los, com o intuito de gerar funções de polarização e difusas, é apresentada e testada em cálculos de propriedades eletrônicas de átomos e moléculas. / Ab initio electronic structure calculations for atoms and especially for molecules are mostly carried out within the finite basis set expansion method in the Hartree-Fock theory by Roothaan. The search for ever more efficient basis sets has been a constant quest and here we show a new alternative to develop efficient Gaussian-Type Functions (GTF) basis sets for atomic and molecular calculations by employing the Polynomial Generator Coordinate Hartree-Fock method.