Thesis (M. Sc.)--University of Alberta, 2009. / Title from PDF file main screen (viewed on Oct. 20, 2009). A thesis submitted to the Faculty of Graduate Studies and Research in partial fulfillment of the requirements for the degree of Master of Science in Materials Engineering, Department of Chemical and Materials Engineering, University of Alberta. Includes bibliographical references.

Thesis (M.Phil.)--University of Hong Kong, 2000. / Includes bibliographical references (leaves 140-141) Also available in print.

Thesis (M.S. in computer science)--Washington State University, December 2005. / Includes bibliographical references.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1982. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 197-201).

Thesis (Ph. D.)--University of Texas at Austin, 2006. / Vita. Includes bibliographical references.

Thesis (Ph. D.)--University of Chicago, 1918. / "Private Edition, Distributed by the University of Chicago Libraries, Chicago, Illinois, 1921." "Reprinted from the Journal of the American Chemical Society, Vol. XXXVIII, February, 1916; Vol. XXXIX, March, 1917; Vol. XLI, April, 1919." Includes bibliographical references. Also available on the Internet.

Dans le cadre du renouvellement du parc nucléaire, six modèles de réacteurs de 4ème génération ont été proposés, dont le Réacteur à Sels Fondus. Ce réacteur a la particularité d’utiliser un combustible à base de fluorures fondus, type LiF-ThF4. Pour développer ce concept, il est important de caractériser d’un point de vue structural ces mélanges de fluorures fondus, pour remonter aux propriétés physico-chimiques du combustible et optimiser ce procédé. Les systèmes fondus MF-ZrF4 (M = Li, Na, K), choisis comme modèle des systèmes au thorium, ont été étudiés expérimentalement par Résonance Magnétique Nucléaire et Absorption des Rayons X à hautes températures, ainsi que par calcul de dynamique moléculaire, en s’intéressant plus particulièrement aux environnements locaux du fluor et du zirconium. Afin d’interpréter les données RMN recueillies dans les milieux fondus, une étude préliminaire sur des halogénures de zirconium et des fluorozirconates de terres rares et d’alcalins solides a été menée par RMN du zirconium 91Zr et des corrélations structures/ paramètres RMN ont été établies. A haute température, dans les systèmes MF-ZrF4 on montre la coexistence de différents complexes du zirconium, avec des coordinences comprises entre 6 et 8, leurs proportions évoluant en fonction de la teneur en ZrF4 du mélange, et du type de l’alcalin. En fonction de la teneur en fluorure de zirconium, nous avons mis en évidence le rôle du fluor dans le bain fondu : fluor libre à faible teneur, il intervient progressivement dans la formation des complexes pour devenir pontant à plus haute teneur. Cette approche originale et innovante des systèmes fluorés fondus, combinant RMN et EXAFS à haute température, avec les calculs de dynamique moléculaire, s’avère particulièrement efficace pour leur description structurale, permettant ainsi de remonter à des données fondamentales, telles que leur spéciation ou leur fluoroacidité. / In the frame of the renewal of the different nuclear plans, the molten salt reactor is one of the six concepts of reactors of IVth generation. This reactor has the particularity to use a liquid fuel based on LiF-ThF4 mixtures. In order to develop and to optimize this concept, it is important to characterize the structure of the melt and to describe its physical and chemical properties. Our work has been based on the study of the system MF-ZrF4 (M = Li, Na, K) selected as a model of ThF4 based systems. We have combined two spectroscopic techniques, the Nuclear Magnetic Resonance and the X-ray Absorption at high temperature, with molecular dynamics calculations. We particularly focused on the local environnements of the fluorine and the zirconium. In order to interpret the NMR data obtain in the molten state, we performed a preliminary study on zirconium halides and rare earth and alkali fluorozirconates using the 91Zr solid-state NMR at very high magnetic fields. New correlations between structural parameters and NMR data have been established. At high temperature, in MF-ZrF4 melts we have shown the coexistence of three different kind of Zr-based complexes with different proportions depending on the amount of ZrF4 and on the nature of the alkali. Depending on the ZrF4 content, three kinds of fluorine have been characterized: form free fluorines at low amount of zirconium fluorides, fluorines involved in Zr-based complexes and bridging fluorines at higher ZrF4 content. This original and innovative approach of molten fluorides mixtures, combining NMR and EXAFS at high temperature with molecular dynamics calculations, is very efficient to describe their speciation and thus their fluoro-acidity.

Computer simulation techniques for exploring the microscopic world are quickly gaining popularity as a tool to complement theoretical and experimental approaches. Molecular dynamics (MD) simulations allow the motion of an N–body soft matter system to be solved using a classical mechanics description. The scope of these simulations are however limited by the available computational power, requiring the development of multiscale methods to make better use of available resources. Dual scale models are a novel form of molecular model which simultaneously feature particles at two levels of resolution. This allows a combination of atomistic and coarse-grained (CG) force fields to be used to describe the interactions between particles. By using this approach, targeted details in a molecule can be described at high resolution while other areas are treated with fewer degrees of freedom. This approach aims to allow for simulating the key features of a system at a reduced computational cost. In this thesis, two generations of a methodology for constructing dual scale models are presented and applied to various materials including polyamide, polyethene, polystyrene and octanol. Alongside a variety of well known atomistic force fields, these models all use iterative Boltzmann inversion (IBI) force fields to describe the CG interactions. In addition the algorithms and data structures for implementing dual scale MD are detailed, and expanded to include a multiple time step (MTS) scheme for optimising its peformance. Overall the IBI and atomistic force fields were compatible with each other and able to correctly reproduce the expected structural results. The first generation methodology featured bonds directly between atoms and beads, however these did not produce the correct structures. The second generation used only atomistic resolution bonds and this improved the intramolecular structures greatly for a relatively minor cost. In both the polyamide and octanol systems studied, the models were also able to properly describe the hydrogen bonding. For the CG half of the force field, it was possible to either use preexisting force field parameters or develop new parameters in situ. The resulting dynamical behaviour of the models was unpredictable and remains an open question both for CG and dual scale models. The theoretical performance of these models is faster than the atomistic counterpart because of the reduced number of pairwise interactions that must be calculated and this scaling was seen with the proposed reference implementation. The MTS scheme was successful in improving the performance with no effects on the quality of results. In summary this work has shown that dual scale models are able to correctly reproduce the structural behaviour of atomistic models at a reduced computational cost. With further steps towards making these models more accessible, they will become an exciting new option for many types of simulation.

University of Macau / Faculty of Science and Technology / Department of Computer and Information Science

A variational principle is applied to the Schroedinger equation for theXY₂ linear molecule. Trial solutions are synthesized from the nuclear eigenstates, which are assumed to be simple harmonic oscillator eigenstates, and from the unperturbed electronic states, whose azimuthal dependence is known because of the cylindrical symmetry of the field of the nuclei. The secular equation is discussed, and an expression for the Renner splitting of the π state is obtained. / Science, Faculty of / Physics and Astronomy, Department of / Graduate