published_or_final_version / abstract / Chemistry / Doctoral / Doctor of Philosophy

published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy

Over the years electronic structure theory has proven to be a powerful method with which one can probe the behaviour of materials, making it possible to describe and predict material properties. The numerical tools needed for these methods are always in need of development, since the desire to calculate more complex materials pushes this field forward. This thesis contains work on both this implementational and developmental aspects. It begins by reviewing density functional theory and dynamical mean field theory, with the aim of merging these two methods. We point out theoretical and technical issues that may occur while doing this. One issue is the Padé approximant, which is used for analytical continuation. We assess the approximant and point out difficulties that can occur, and propose and evaluate methods for their solution. The virial theorem is assessed within the framework of density functional theory merged with many-body methods. We find that the virial theorem is extended from its usual form, and confirm this by performing practical calculations. The unified theory of crystal structure for transition metals has been established a long time ago using early electronic structure calculations. Here we implement the first- principles exact muffin-tin orbitals method to investigate the structural properties of the 6d transition metals. The goal of our study is to verify the existing theory for the mostly unknown 6d series and the performance of the current state-of-the art in the case of heavy d metals. It is found that these elements behave similarly to their lighter counterparts, except for a few deviations. In these cases we argue that it is relativistic effects that cause this anomalous behaviour. Palladium is then studied, taking many-body effects into account. We find that we can reproduce experimental photoemission spectra by these methods, as well as the Fermi surface. The thesis ends with an investigation of the stacking fault energies of the strongly correlated metal cerium. In addition to providing the first ab-initio stacking fault data for the two cubic phases of Ce, we discuss how these results could have an impact on the interpretation of the phase diagram of cerium / <p>QC 20150522</p>

This is a study of the structural and electronic behavior and properties of graphene on α-quartz and α-sapphire using Density Functional Theory. We construct initial structures using the above 2 substrates, place a layer of graphene on them and subsequently allow the atoms to relax. After relaxation we study any structural changes, band structures, density of states, charge density to determine the electronic properties of the entire structure. Eventually this study will help in the search for good substrates for graphene based transistors. / text

Since the 1987 Brundtland Report, the development of urban areas has been considered a key determinant in achieving 'sustainability'. Greater residential density is increasingly advocated for and applied through policy statements around the world as a way of achieving this goal. Various tiers of New Zealand government are following international policy trends, developing programmes, protocols and strategies that promote sustainability and 'good' urban design practices through intensification, or concentration, within urban areas. Research shows that a policy framework of urban concentration, through greater residential density, is only successful where consumers and providers of housing support its practical application. Confrontation between policy and the market, and the acceptability of greater levels of residential density to residents, can jeopardise a policy's success. This research uses a mix of survey and interview techniques to determine the acceptability of "medium density" developments to residents, and to understand the practises and motivations of housing developers in Christchurch's "Living 3" zone. This zone is predominantly sited between the central business district and low-density suburban areas, making it ideally located to facilitate policies of intensification. The principle purpose of the zone is the development of medium-density residential accommodation, however greater residential density is relatively new to Christchurch where the potential for expansion is seemingly unbounded. The intention of this research is to assist the planning, production and performance of future developments. In conclusion, this thesis makes recommendations to improve the form and design of medium density residential developments in Christchurch's inner Living Three zone in terms of the market's producers and consumers.

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Three studies were conducted to determine whether the elevated plasma and HDL cholesterol levels observed in copper-deficient rats could be explained by the interaction of ¹²⁵I-HDL subfractions with liver membrane preparations in vitro. Rats from all studies were randomly divided into two dietary treatments, copper-deficient and adequate (0.7 mg and 8.0 mg Cu/kg diet, respectively). Deionized water and diet were provided ad libitum. After eight weeks, rats were exsanguinated, membranes prepared from livers, and plasma high density lipoproteins (HDL) isolated by ultracentrifugation and agarose column chromatography. Heparin-Sepharose affinity chromatography was used to isolate specific subfractions of HDL. The HDL subfractions derived from rats of each dietary treatment were iodinated and bound to either crude liver membranes or purified liver plasma membranes prepared from rats of both treatment groups. Total binding data and computer derived estimates (K(d) and B(max)) were used to compare differences between treatments. Binding data from all experiments conformed to a one-site model. In all cases, binding was saturable and EDTA and pronase insensitive. Treatment differences were observed in Study I (¹²⁵I-apo E-free HDL binding to crude liver membranes). Significantly lower total binding and B(max) were observed when lipoproteins and membranes from copper-deficient animals were used in the assay. Competition experiments from Studies II and III demonstrate that the different HDL subfractions competed effectively with one another for binding sites, indicating that apo E is not a determinant in binding of rat ¹²⁵I-HDL subfractions to purified liver plasma membranes.

Parametric excitation and dispersal are added to discrete-time population models. Discrete-time models for growth with dispersal share many of the attributes of reaction-diffusion equations. At the same time, these models readily exhibit period doubling and chaos. Large parametric excitation (seasonality) is inevitably destabilizing, but mild seasonality may have a pronounced stabilizing effect. Seasonality also allows for the coexistence of alternative stable states (equilibria, cycles, chaos). Many examples are presented.