Yim Wai-leung. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1999. / Includes bibliographical references (leaves 73-77). / Abstracts in English and Chinese. / THESIS COMMITTEE --- p.ii / ABSTRACT (English version) --- p.iii / ABSTRACT (Chinese version) --- p.v / ACKNOWLEDGEMENTS --- p.vi / TABLE OF CONTENTS --- p.vii / LIST OF FIGURES --- p.ix / LIST OF TABLES --- p.xi / Chapter CHAPTER 1. --- General Introduction / Chapter Section 1.1 --- Introduction --- p.1 / Chapter Section 1.2 --- Electronic Structure Calculation / Chapter 1.2.1 --- Density Functional Theory --- p.2 / Chapter 1.2.2 --- "Exchange, Correlation and the Local Density Approximation" --- p.4 / Chapter 1.2.3 --- Bloch's Theorem and Plane Wave Basis Set --- p.6 / Chapter 1.2.4 --- The Pseudopotential Approximation --- p.10 / Chapter Section 1.3 --- Molecular Dynamics / Chapter 1.3.1 --- Molecular Dynamics --- p.12 / Chapter 1.3.2 --- Nose Thermostat / Chapter 1.3.2.1 --- Introduction --- p.14 / Chapter 1.3.2.2 --- Feedback Method --- p.15 / Chapter Section 1.4 --- Case Studies / Chapter 1.4.1 --- Thermal properties of small silver clusters --- p.18 / Chapter 1.4.2 --- Thermal decomposition channels of NTO --- p.20 / Chapter CHAPTER 2. --- Ab Initio Molecular Dynamics Study on Agn (n=4-6) / Chapter Section 2.1 --- Introduction --- p.22 / Chapter Section 2.2 --- Computational Method --- p.24 / Chapter Section 2.3 --- Results and Discussion / Chapter 2.3.1 --- Ag2 --- p.26 / Chapter 2.3.2 --- Ag4 --- p.30 / Chapter 2.3.3 --- Ag5 --- p.36 / Chapter 2.3.4 --- Ag6 --- p.45 / Chapter Section 2.4 --- Summary --- p.49 / Chapter CHAPTER 3. --- Ab Initio Molecular Dynamics Study on Thermal Decomposition of NTO / Chapter Section 3.1 --- Introduction --- p.52 / Chapter Section 3.2 --- Computation Details --- p.55 / Chapter Section 3.3 --- Results and Discussion / Chapter 3.3.1 --- Comparison of the Quantum Calculations by VASP and Gaussian98 --- p.56 / Chapter 3.3.2 --- Exploring the Reaction Channels --- p.62 / Chapter 3.3.2.1 --- Hydrogen-transfer Activation --- p.62 / Chapter 3.3.2.2 --- Homolytic Cleavage of C-N02 Bond --- p.63 / Chapter 3.3.2.3 --- Nitro-nitrite Rearrangement --- p.64 / Chapter 3.3.2.4 --- Direct Ring Rupture --- p.64 / Chapter 3.3.3 --- Energetic Consideration --- p.65 / Chapter 3.3.4 --- Activation Barriers --- p.70 / Chapter 3.3.5 --- Summary --- p.72 / REFERENCES --- p.73

New thin-film solar cell materials and a greater understanding of their properties are needed to meet the urgent demand for sustainable, lower-cost and scalable photovoltaics. Computational techniques have been used to investigate Cu2ZnSnS4, CuSbS2 and CuBiS2 , which are potential absorber layer materials in thin-film photovoltaics. Their low cost, low toxicity and their constituent’s relative abundance make them suitable replacements for current thin-film absorbers, which are CdTe or Cu(In, Ga)(S, Se)2 based systems. Firstly, we have used hybrid Density Functional Theory (DFT) calculations to study CuSbS2 and CuBiS2. We calculate band gaps of 1.69 eV and 1.55 eV respectively, placing CuBiS2 within the optimal range for a viable absorber material. The density of states for both these materials indicate that formation of electron hole charge carriers will occur in the Cu d10 band. Consequently, photoexcitation leads to the oxidation of Cu(I). Secondly, we have derived interatomic potentials which describe the complex structure of Cu2ZnSnS4 accurately. We find that the Cu/Zn antisite defect represents the lowest energy form of intrinsic defect disorder. For these antisite defects, we find a preference for small neutral defect clusters, which suggests a degree of self-passivation exists. Investigations of Cu-ion transport find VCu migration is possible via a vacancy hopping mechanism. There are pathways which can be connected to give 3D long-range diffusion. Investigations of the Cu/Zn site disorder in Cu2ZnSnS4 find that configurations which are kesterite-like will dominate synthetic samples. However, perfectly ordered kesterite will not be formed due to entropic effects. The simulations indicate the stannite and stannite-like polymorphs are less favourable, and can only account for ≈2.5% of a sample. Investigations of the surfaces of Cu2ZnSnS4, suggest that the vast majority of the low index surfaces are dipolar and that only the (1 1 2), (0 1 0) and (1 0 1) surfaces have low surface energies.

Cheung Chung Hong. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2005. / Includes bibliographical references (leaves 126-137). / Abstracts in English and Chinese. / ABSTRACT (English version) --- p.iii / ABSTRACT (Chinese version) --- p.vi / ACKNOWLEDGMENTS --- p.viii / TABLE OF CONTENTS --- p.ix / LIST OF FIGURES --- p.xiii / LIST OF TABLES --- p.xvii / Chapter CHAPTER ONE: --- INTRODUCTION --- p.1 / Chapter 1.1 --- Molecular Structure Determination --- p.1 / Chapter 1.2 --- Methods for Structure Determination --- p.1 / Chapter 1.2.1 --- Infrared (IR) Spectroscopy --- p.1 / Chapter 1.2.2 --- Electron Microscopy (EM) --- p.2 / Chapter 1.2.3 --- X-ray Diffraction (XRD) --- p.2 / Chapter 1.2.4 --- Nuclear Magnetic Resonance (NMR) Spectroscopy --- p.3 / Chapter 1.3 --- Solid State NMR Spectroscopy 一 Chemical Shielding Tensor --- p.4 / Chapter 1.4 --- Scope of This Thesis --- p.6 / Chapter CHAPTER TWO: --- PRINCIPLE AND THEORY --- p.7 / Chapter 2.1 --- Introduction --- p.7 / Chapter 2.2 --- Chemical Shielding Tensor (CST) --- p.7 / Chapter 2.2.1 --- Basis of Nuclear Magnetic Resonance --- p.7 / Chapter 2.2.2 --- Theoretical Description of CST --- p.8 / Chapter 2.3 --- CST Calculation --- p.11 / Chapter 2.3.1 --- Ramsey's Theory --- p.11 / Chapter 2.3.2 --- Gauge-including Atomic Orbitals (GIAO) Method --- p.13 / Chapter 2.4 --- Density Functional Theory (DFT) --- p.14 / Chapter 2.4.1 --- KS Theorem --- p.14 / Chapter 2.4.2 --- B3LYP - Hybrid DFT Functional --- p.16 / Chapter 2.5 --- Molecular Mechanic (MM) --- p.16 / Chapter 2.5.1 --- Basis Principle 一 Ball and Spring Model --- p.16 / Chapter 2.5.2 --- MM+ --- p.18 / Chapter 2.5.2.1 --- Bond Stretching --- p.18 / Chapter 2.5.2.2 --- Bond Bending --- p.19 / Chapter 2.5.2.3 --- Torsional Motion --- p.19 / Chapter 2.5.2.4 --- van der Waals Interaction --- p.19 / Chapter 2.5.2.5 --- Electrostatic Interaction --- p.20 / Chapter 2.5.2.6 --- Stretching-bending Interaction --- p.21 / Chapter 2.6 --- Isodesmic Reaction --- p.21 / Chapter CHAPTER THREE: --- METHODOLOGY AND EVALUATION --- p.23 / Chapter 3.1 --- Introduction --- p.23 / Chapter 3.2 --- Computational Method --- p.24 / Chapter 3.2.1 --- Evaluation of Different NMR Computation Level --- p.24 / Chapter 3.2.2 --- Computational Error 一 Round Off Error --- p.32 / Chapter 3.3 --- Local Structure Determination and Evaluation --- p.34 / Chapter 3.3.1 --- Methodology --- p.34 / Chapter 3.3.2 --- Definition of Local Structure --- p.37 / Chapter 3.3.3 --- Models used in Local Structure Determination --- p.37 / Chapter 3.3.3.1 --- Model without CST Modification (Mod-1) --- p.38 / Chapter 3.3.3.2 --- Models with CST Modification --- p.39 / Chapter 3.3.3.2.1 --- Model Using Correction Factors (Mod-2) --- p.39 / Chapter 3.3.3.2.2 --- Model Using Linear Equation (Mod-3) --- p.40 / Chapter 3.3.4 --- Evaluation - Me2P(S)C(OH)R1R2 --- p.41 / Chapter 3.4 --- Determination of Possible Conformation in Powder and Evaluation --- p.53 / Chapter 3.4.1 --- Introduction --- p.53 / Chapter 3.4.2 --- Methodology --- p.54 / Chapter 3.4.2.1 --- Preparation of Calibration Curve --- p.54 / Chapter 3.4.2.2 --- Determination of Possible Conformation Contributing to the Observed CST --- p.57 / Chapter 3.4.3 --- Evaluation --- p.59 / Chapter 3.5 --- Discussion --- p.72 / Chapter 3.5.1 --- Factors Affecting CST --- p.72 / Chapter 3.5.1.1 --- Inter-molecular Interaction --- p.72 / Chapter 3.5.1.1.1 --- O-H----S --- p.73 / Chapter 3.5.1.1.2 --- C-H----S --- p.78 / Chapter 3.5.1.1.3 --- van der Waals Forces --- p.80 / Chapter 3.5.1.2 --- Conformation --- p.81 / Chapter 3.5.2 --- Effect of Experimental Error on the Calculated Structure --- p.82 / Chapter 3.6 --- Summary --- p.84 / Chapter CHAPTER FOUR: --- APPLICATIONS --- p.86 / Chapter 4.1 --- Introduction --- p.86 / Chapter 4.2 --- Tetramethyldiphoshine Disulfide (TMPS) --- p.86 / Chapter 4.2.1 --- Local Structure --- p.87 / Chapter 4.2.2 --- Conformation --- p.92 / Chapter 4.3 --- "Carbon Compounds : 1,3,5-Trimethoxybenzene (1,3,5-TMB) and 1,4-Dimethoxybenzene (1,4-DMB)" --- p.97 / Chapter 4.3.1 --- Local Structure --- p.98 / Chapter 4.3.2 --- Conformation --- p.103 / Chapter 4.4 --- Conclusion --- p.110 / Chapter CHAPTER FIVE: --- CONCLUSIONS --- p.111 / APPENDIX --- p.114 / REFERENCES --- p.126

Hu Hong Bing. / "May 2004." / "13" in title is superscript. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2004. / Includes bibliographical references. / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Mode of access: World Wide Web. / Abstracts in English and Chinese.

In the first part, the mechanisms for the dissociation of TPA are studied under three types of conditions. The unimolecular dissociation is initiated by the breaking of either the N-Calpha and Calpha -Cbeta bonds and leads to many complicated processes. Within the confined space inside neutral zeolite channels, the diffusion of H radicals enhances a cycle of reactions, which accounts for the experimental observation of dipropylamine and monopropylamine. In the presence of an acidic site, the dissociation of TPA goes through catalyzed successive steps to produce ammonia and propylene molecules. / In the last part, two distinct paths are proposed to investigate the carbon nanotube growth mechanism using benzene as the growth seed and propylene as carbon resource. There is an incremental aromatization process, involving both alkylation and dehydrogenation, that leads to linked aromatic rings to form either (3,3) tube or (4,2) tube. Two paths are identified, one via toluene and the other via cumene. The cumene path is more favorable as the barrier is significant lower. / In the second part, A T5 cluster model is used to investigate mechanisms of propylene aromatization to benzene, which involves chemisorption, dimerization, cyclization and dehydrogenation. Propylene can be chemisorbed to form two distinct products, n-propoxide and i-propoxide, which can further be dimerizated to form longer chain olefins 1-hexene and 2-hexene (from n-propoxide), and 4-methyl-1-pentene and 4-methyl-2-penetene (from i-propoxide). Initiated by H2 elimination, these dimerization products can further go through cyclization process to generated either 6-member ring cyclohexene or 5-member ring methyl-cyclopentene. Catalyzed by zeolite, cyclohexene can directly dehydrogenate to form benzene whereas methyl-cyclopentene can dehydrogenate to form fulven, an isomer to benzene. Under acidic zeolite environment, a fulvene can readily be transformed to the thermodynamically more stable benzene. / The growth mechanisms of mono-sized and parallel-aligned single wall carbon nanotube (CNT) in the microporous channels of AlPO4-5 are investigated by density functional theory calculations. Detailed mechanisms are proposed for the decomposition of TPA, the formation of aromatic ring, and the growth of carbon nanotubes. / Liu, Jianwen. / Adviser: Zhifeng Liu. / Source: Dissertation Abstracts International, Volume: 70-09, Section: B, page: . / Thesis submitted in: December 2008. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2009. / Includes bibliographical references (leaves 98-99). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstracts in English and Chinese. / School code: 1307.

We consider the structural and physical properties of complex model morphologies and microstructures obtained by Xray-CT imaging. The Minkowski functionals, a family of statistical measures based on the Euler-Poincar&eacute characteristic of n-dimensional space, are shown to be sensitive measures of the morphology of disordered structures. Analytic results for the Boolean model are given and used to devise a reconstruction scheme, which allows one to accurately reconstruct a complex Boolean structure given at any phase fraction for all other phase fractions. The percolation thresholds of either phase are obtained with good accuracy. From the reconstructions one can subsequently predict property curves for the material across all phase fractions from a single 3D image. We illustrate this for transport and mechanical properties of complex Boolean systems and for experimental sandstone samples. By extending the Minkowski functionals to parallel surfaces using operations from mathematical morphology, a powerful discrimination of structure is obtained. Further the sensitivity of the Minkowski functionals under experimental conditions is analysed. Accurate calculations of conductive and elastic properties directly from tomographic images are achieved by estimating and minimising several sources of numerical error. Simulations of electrical conductivity and linear elastic properties on microtomographic images of Fontainebleau sandstone are in excellent agreement with experimental measurements over a wide range of porosity. The results show the feasibility of combining digitised images with transport and elasticity calculations to accurately predict physical properties of individual material morphologies. We show that measurements of properties based on microtomographic images are more accurate than those based on conventional theories for disordered materials. We study the elastic behaviour of model clean and cemented sandstones. Results are in excellent agreement with available experimental data, and are compared to conventional theoretical and empirical laws. A new predictive empirical method is given for predicting the elastic moduli of sandstone morphologies. The method gives an excellent match to numerical and experimental data.

Mixed-valence compounds are of interest as model systems for the study of electron transfer reactions. The intramolecular electron transfer processes and patterns of charge delocalization in such compounds depend on the interplay between the electronic (V) and the vibronic (L) coupling. One can obtain both parameters from a Hush analysis of the intervalence band that arises upon optical intramolecular electron transfer if the band is intense and well-separated from other bands. This is quite often the case for mixed-valence triarylamines. As such, both Hush analysis and simulation of the intervalence band are widely used to classify these compounds as charge localized (class-II) or delocalized (class-III). Yet one must estimate the diabatic electron transfer distance (R) to calculate V in the Hush formalism. For mixed-valence triarylamines, R is commonly taken as the N-N distance; we show this to be a poor approximation in many cases. The activation barrier to thermal intramolecular electron transfer in a class-II mixed-valence compound is also related to the parameters V and L. Thus, if one can capture the rate of thermal electron transfer at multiple temperatures, then two experimental methods exist by which to extract the microscopic parameters. One technique that is widely used for organic mixed-valence compounds is variable-temperature electron spin resonance (ESR) spectroscopy. But this method is only rarely used to determine thermal electron transfer rates in mixed-valence triarylamines, as the electron transfer in most of the class-II compounds with distinct intervalence bands is too fast to observe on the ESR timescale. We show, for the first time, that one can use ESR spectroscopy to measure thermal electron transfer rates in such compounds. Simulation of ESR spectra based on density functional theory calculation and comparison with optical data also uncover the nature (i.e., adiabatic or nonadiabatic) of the electron transfer process.

The distinct response of biological systems to the two enantiomers of a chiral chemical has led to a large market for enantiopure pharmaceuticals and raised fundamental issues about the origin of biological homochirality. It is therefore important to understand the interactions of chiral molecules with chiral environments. Chiral environments associated with solid surfaces could potentially play a useful role in chirally specific chemical processing. There are a variety of routes for creating chiral solid surfaces. Surfaces of materials whose bulk crystal structure is enantiomorphic can be used as one type of chiral solid surfaces. Metal surfaces that are intrinsically chiral due to the presence of kinked surface steps provide another route for creating chiral solid surfaces. Alternatively, we can impart chirality onto surfaces by attaching irreversibly adsorbing chiral organic species on otherwise achiral surfaces. Understanding and ultimately controlling enantiospecific interactions of molecules on this kind of surfaces requires detailed insight into the adsorption geometries and energies of these complex interfaces. To tackle these issues, we performed density functional theory (DFT) calculations that have proved to be a useful tool for quantitative prediction of these effects. Besides our main topic above, we theoretically examine the effects of K atoms as a promoter coadsorbed with small molecules on Mo2C surfaces, a promising catalyst for a range of chemicals applications. Our results in this thesis provide fundamental information about these systems and demonstrate that using DFT for this purpose can be a useful means of identifying the phenomena that control chiral surface chemistry.

The interface of a zinc-terminated polar zinc oxide surface (0002) with a series of chemisorbed fluorinated benzylphosphonic acids has been studied using density functional theory. The calculations indicate that there is a substantial change in the binding energies and work function modification depending on the binding motif. The results also indicate that there is a pronounced difference in the magnitude and trends of the factors determining the total change in work function. The oxygen core-level binding shifts have been calculated and compared to available experimental data.

Thesis (Ph. D.)--University of Washington, 2001. / Vita. Includes bibliographical references (p. 129-136).