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).

Thesis (M. Phil.)--University of Hong Kong, 2001. / Includes bibliographical references (leaves 81-86).

We present a theoretical study of the electronic structure, surface energies and work functions of orthorhombic Pt monosilicide and germanides of Pt, Ni, Y and Hf within the framework of density functional theory (DFT). Calculated work functions for the (001) surfaces of PtSi, NiGe and PtGe suggest that these metals and their alloys can be used as self-aligned contacts to p-type silicon and germanium. In addition, we also study electronic structure and calculate the Schottky-barrier height at Si(001)/PtSi(001) interface and GaAs(001)/NiPtGe(001) interfaces with different GaAs(001) and NiPtGe (001) terminations. The p-type Schottky barrier height of 0.28 eV at Si/PtSi interface is found in good agreement with predictions of a simple metal induced gap states (MIGS) theory and available experiment. This low barrier suggests PtSi as a low contact resistance junction metal for silicon CMOS technology. We identify the growth conditions necessary to stabilize this orientation. The calculated p-type Schottky barrier heights (SBH) at different GaAs/NiPtGe interfaces vary by as much as 0.18 eV around the average value of 0.5 eV. We further identify and discuss factors responsible for strong Fermi level pinning resulting in small variation in the p-SBH. We also present a theoretical study of magnetic state of [beta]-MaAs and show that it is antiferromagnetic and explain the lack of observed long-range order.

published_or_final_version / abstract / toc / Chemistry / Doctoral / Doctor of Philosophy

published_or_final_version / Chemistry / Master / Master of Philosophy

Using computational methods, the formation pathways and structures of four experimentally-observed DNA intrastrand cross-links are determined. These lesions originate from the uracil radical and are of particular importance due to their potential role in the activity of the 5-halouracils as radiosensitizing agents in anti-tumour treatments. The formation pathways are studied with density functional theory under conditions relevant to both UV and ionizing radiation. Results reveal these intrastrand cross-links are likely to form under therapeutic conditions and provide an explanation for their observed formation preferences. The structures of the cross-links in DNA are determined with molecular dynamics simulations to reveal the distortions these lesions induce to the helix. This has provided information about the potential biological implications of these lesions, where results indicate intrastrand cross-links are likely both mutagenic and cytotoxic. Therefore, these lesions may contribute to tumour cell death in the therapeutic use of halouracils. / xvi, 147 leaves : ill. (chiefly col.) ; 29 cm + 1 CD-ROM

Thesis (Ph. D.)--University of Texas at Austin, 2007. / Vita. Includes bibliographical references.

Thesis (M. Phil.)--University of Hong Kong, 2008. / Includes bibliographical references (leaf 76-77) Also available in print.