Diffusive Molecular Dynamics (DMD) is a class of recently developed computational methods for the simulation of long-term mass transport with a full atomic fidelity. Its basic idea is to couple a discrete kinetic model for the evolution of mass transport process with a non-equilibrium thermodynamics model that governs lattice deformation and supplies the requisite driving forces for kinetics. Compared to previous atomistic models, e.g., accelerated Molecular Dynamics and on-the-fly kinetic Monte Carlo, DMD allows the use of larger time-step sizes and hence has a larger simulation time window for mass transport problems. This dissertation focuses on the development, assessment and application of a DMD computational framework for the long-term, three-dimensional, deformation-diffusion coupled analysis of solute mass transport in nanomaterials. First, a computational framework is presented, which consists mainly of: (1) a computational model for interstitial solute diffusion, which couples a nonlinear optimization problem with a first-order nonlinear ordinary differential equation; (2) two numerical methods, i.e., mean field approximation and subcycling time integration, for accelerating DMD simulations; and (3) a high-performance computational solver, which is parallelized based on Message Passing Interface (MPI) and the PETSc/TAO library for large-scale simulations. Next, the computational framework is validated and assessed in two groups of numerical experiments that simulate hydrogen mass transport in palladium. Specifically, the framework is validated against a classical lattice random walk model. Its capability to capture the atomic details in nanomaterials over a long diffusive time scale is also demonstrated. In these experiments, the effects of the proposed numerical methods on solution accuracy and computation time are assessed quantitatively. Finally, the computational framework is employed to investigate the long-term hydrogen absorption into palladium nanoparticles with different sizes and shapes. Several significant findings are shown, including the propagation of an atomistically sharp phase boundary, the dynamics of solute-induced lattice deformation and stacking faults, and the effect of lattice crystallinity on absorption rate. Specifically, the two-way interaction between phase boundary propagation and stacking fault dynamics is noteworthy. The effects of particle size and shape on both hydrogen absorption and lattice deformation are also discussed in detail. / Ph. D. / Interstitial diffusion in crystalline solids describes a phenomenon in which the solute constituents (e.g., atoms) move from an interstitial space of the host lattice to a neighboring one that is empty. It is a dominating feature in many important engineering applications, such as metal hydrides, lithium-ion batteries and hydrogen-induced material failures. These applications involve some key problems that might take place over long time periods (e.g., longer than 1 s), while the nanoscale behaviors and mechanisms become significant. The time scale of these problems is beyond the capability of established atomistic models, e.g., accelerated Molecular Dynamics and on-the-fly kinetic Monte Carlo. To this end, this dissertation presents the development and application of a new computational framework, referred to as Diffusive Molecular Dynamics (DMD), for the simulation of long-term interstitial solute diffusion in advanced nanomaterials. The framework includes three key components. Firstly, a DMD computational model is proposed, which accounts for three-dimensional, deformation-diffusion coupled analysis of interstitial solute mass transport. Secondly, nu- merical methods are employed to accelerate the DMD simulations while maintaining a high solution accuracy. Thirdly, a high-performance computational solver is developed to implement the DMD model and the numerical methods. Moreover, regarding its application, the DMD framework is first validated and assessed in the numerical experiments pertaining to hydrogen mass transport in palladium crystals. Then, it is employed to investigate the atomic behaviors and mechanisms involved in the long-term hydrogen absorption by palladium nanoparticles with different sizes and shapes. The two-way interaction between hydrogen absorption and lattice deformation is studied in detail.

Steepest-entropy-ascent quantum thermodynamics (SEAQT) is a mathematical and theoretical framework for intrinsic quantum thermodynamics (IQT), a unified theory of quantum mechanics and thermodynamics. In the theoretical framework, entropy is viewed as a measure of energy load sharing among available energy eigenlevels, and a unique relaxation path of a system from an initial non-equilibrium state to a stable equilibrium is determined from the greatest entropy generation viewpoint. The SEAQT modeling has seen a great development recently. However, the applications have mainly focused on gas phases, where a simple energy eigenstructure (a set of energy eigenlevels) can be constructed from appropriate quantum models by assuming that gas-particles behave independently. The focus of this research is to extend the applicability to solid phases, where interactions between constituent particles play a definitive role in their properties so that an energy eigenstructure becomes quite complicated and intractable from quantum models. To cope with the problem, a highly simplified energy eigenstructure (so-called ``pseudo-eigenstructure") of a condensed matter is constructed using a reduced-order method, where quantum models are replaced by typical solid-state models. The details of the approach are given and the method is applied to make kinetic predictions in various solid-state phenomena: the thermal expansion of silver, the magnetization of iron, and the continuous/discontinuous phase separation and ordering in binary alloys where a pseudo-eigenstructure is constructed using atomic/spin coupled oscillators or a mean-field approximation. In each application, the reliability of the approach is confirmed and the time-evolution processes are tracked from different initial states under varying conditions (including interactions with a heat reservoir and external magnetic field) using the SEAQT equation of motion derived for each specific application. Specifically, the SEAQT framework with a pseudo-eigenstructure successfully predicts: (i) lattice relaxations in any temperature range while accounting explicitly for anharmonic effects, (ii) low-temperature spin relaxations with fundamental descriptions of non-equilibrium temperature and magnetic field strength, and (iii) continuous and discontinuous mechanisms as well as concurrent ordering and phase separation mechanisms during the decomposition of solid-solutions. / Ph. D. / Many engineering materials have physical and chemical properties that change with time. The tendency of materials to change is quantified by the field of thermodynamics. The first and second laws of thermodynamics establish conditions under which a material has no tendency to change; these conditions are called equilibrium states. When a material is not in an equilibrium state, it is able to change spontaneously. Classical thermodynamics reliably identifies whether a material is susceptible to change, but it is incapable of predicting how change will take place or how fast it will occur. These are kinetic questions that fall outside the purview of thermodynamics. A relatively new theoretical treatment developed by Hatsopoulos, Gyftopoulos, Beretta and others over the past forty years extends classical thermodynamics into the kinetic realm. This framework, called steepest-entropy-ascent quantum thermodynamics (SEAQT), combines the tools of thermodynamics with quantum mechanics through a postulated equation of motion. Solving the equation of motion provides a kinetic description of the path a material will take as it changes from a non-equilibrium state to stable equilibrium. To date, the SEAQT framework has been applied primarily to systems of gases. In this dissertation, solid-state models are employed to extend the SEAQT approach to solid materials. The SEAQT framework is used to predict the thermal expansion of silver, the magnetization of iron, and the kinetics of atomic clustering and ordering in binary solid-solutions as a function of time or temperature. The model makes it possible to predict a unique kinetic path from any arbitrary, non-equilibrium, initial state to a stable equilibrium state. In each application, the approach is tested against experimental data. In addition to reproducing the qualitative kinetic trends in the cases considered, the SEAQT framework shows promise for modeling the behavior of materials far from equilibrium.

Consumers use batteries daily, and the lithium-ion battery has undergone a lot of engineering advances in the last few decades. There is a need to understand and improve the cathode chemistry to adapt to the rapidly growing electronics and electric vehicle market that is continually demanding more energy from batteries. Nickel-rich layered LiNi_1-x-yMn_xCo_yO₂ (1-x-y ≥ 0.6, NMC) cathodes could potentially provide the necessary energy to meet the demand of the high energy applications. Overcoming the stability issues from oxygen activation in nickel-rich materials is one of the largest challenges facing the commercial incorporation of NMCs. This thesis focuses on, LiNi_0.8Mn_0.1Co_0.1 (NMC811). Using surface sensitive techniques, such as Xray Absorption (XAS), our research reveals that degradation of NMC811 occurs during cycling, regardless of temperature, and that oxygen activation plays a role in the overall surface changes and degradation observed in NMC811. The thesis then explores the role of substituting a transition metal in the NMC811. Then we used a gradient addition of titanium to the NMC811 material to stabilize the battery performance. Theoretical techniques, such as Finite Difference Method Near Edge Structure, and experimental techniques, such as XAS, revealed how transition metal substitution, specifically titanium, stabilized the lattice. The results indicated that titanium deactivates oxygen by limiting the nickel and oxygen covalency that typically leads to oxygen activation upon charging. We observed that the titanium substitution increases cycling reversibility after hundreds of cycles. Overall, the work indicates that a more stable nickel-rich material is possible. It identifies the reasons why substitution can work in cathode materials. Additionally, the methods described can provide a guideline to further studies of stabilization of the cathode. / Master of Science / Consumers across the world use lithium-ion batteries in some fashion in their everyday life. The growing demand for energy has led to batteries dying quicker than consumers want. Thus, there are calls for researchers to develop batteries that are longer lasting. However, the initial increase in battery life over the years has been from better engineering and not necessarily from making a better material for a battery. This thesis focuses on the understanding of the chemistry of the materials of a battery. Throughout the chapters, the research delves into the how and why materials with extra nickel degrade quickly. Then, it investigates a method of making these nickel-rich materials last longer and how the chemistry within these materials are affected by the addition of a different metal. Overall, the findings indicate that the addition of titanium creates a more stable material because it mitigates the release of oxygen and prevents irreversible changes within the structure of the material. It determines that the chemistry behind the failings of nickel-rich lithium-ion batteries and a potential method for allowing the batteries to last longer. It also provides insight and guidance for potential future research of stabilization of lithium-ion materials.

Les films de ZrO2 pur sont déposés par MOCVD (Metal-Organic Chemical Vapor Deposition) en variant de nombreux paramètres du processus. L’influence des conditions de dépôt sur l’évolution de la microstructure (morphologies, structure cristalline/phase, texture et contrainte résiduelle) a été étudiée et clarifiée. Par des analyses approfondies des résultats expérimentaux, trois mécanismes typiques de croissance de dépôt de ZrO2 ont été proposées. Les contraintes de croissance de compression sont en relation directe avec la diffusion atomique et la quantité d’espèces piégées dans les films. La formation de la texture cristallographique est complexe et deux types de textures ont été analysées dans la phase tétragonale : la texture de fibre {1 1 0}t est contribuée par l’effet superplastique des nano-cristallites de ZrO2 et par la contrainte de croissance de compression ; tandis que la morphologie en facette est due à la croissance concurrentielle de différents plans cristallographiques. La stabilisation de la phase tétragonale de ZrO2 a été analysée et discutée. En plus de la taille critique des cristallites, la stabilisation de la phase tétragonale est favorisée par deux autres mécanismes : la grande quantité des défauts cristallins et la morphologie des cristallites. / Pure ZrO2 films were deposited by MOCVD (Metal-Organic Chemical Vapor Deposition) by varying the deposition parameters over large range. The influence of deposition conditions on the evolution of the microstructure (morphology, crystal structure / phase, texture and residual stress) was studied and clarified. Through careful study and analysis of experimental results, three typical mechanisms of deposition of ZrO2 have been proposed. The compressive growth stresses are directly related to atomic diffusion and the trapped-in effects during deposition. The formation of crystallographic texture is complex and two types of textures were analyzed in the tetragonal phase: the fiber texture {1 1 0}t is supposed to be the result of the effect of superplastic of ZrO2 nano-crystallites and the compressive growth stress, while the facet morphology (the {0 1 1}t fiber) is due to the competitive growth of different crystallographic planes. The stabilization of the tetragonal phase of ZrO2 was analyzed and discussed. In addition to the critical size of crystallites, the stabilization of the tetragonal phase can be favored by two mechanisms: the large amount of crystal defects and morphology of crystallites.

La thèse porte sur la modélisation de la transformation de l'austénite en ferrite dans les aciers en mettant l'accent sur les conditions thermodynamiques et cinétiques aux interfaces alpha/gamma en cours de croissance de la ferrite. Dans une première partie, la thèse se concentre sur la description des équilibres thermodynamiques entre alpha et gamma à l'aide de la méthode CalPhad. Nous avons développé un nouvel algorithme hybride combinant la construction d'une enveloppe convexe avec la méthode classique de Newton-Raphson. Nous montrons ses possibilités pour des aciers ternaire Fe-C-Cr et quaternaire Fe-C-Cr-Mo dans des cas particulièrement difficiles. Dans un second chapitre, un modèle à interface épaisse a été développé. Il permet de prédire l'ensemble du spectre des conditions à l'interface alpha/gamma au cours de la croissance de la ferrite, de l'équilibre complet au paraéquilibre avec des cas intermédiaires des plus intéressants. Nous montrons que de nombreux régimes cinétiques particuliers dans les systèmes Fe-C-X peuvent être prévus avec un minimum de paramètres d'ajustement, principalement le rapport entre les diffusivités de l'élément substitutionnel dans l'interface épaisse et dans le volume d'austénite. Le troisième chapitre porte sur l'étude d'un modèle de champ de phase. Une analyse approfondie des conditions à l'interface données par le modèle est réalisée en utilisant la technique des développements asymptotiques. En utilisant les connaissances fournies par cette analyse, le rôle de la mobilité intrinsèque d'interface sur la cinétique et les régimes de croissance est étudié, à la fois dans le cas simple d'alliages binaires Fe-C et dans le cas plus complexe d'alliages Fe-C-Mn / Transformation in steels focusing on the thermodynamic and kinetics conditions at the alpha/gamma interfaces during the ferrite growth. The first chapter deals with the determination of thermodynamic equilibria between alpha and gamma with CalPhad thermodynamic description. We have developed a new hybrid algorithm combining the construction of a convex hull to the more classical Newton-Raphson method to compute two phase equilibria in multicomponent alloys with two sublattices. Its capabilities are demonstrated on ternary Fe-C-Cr and quaternary Fe-C-Cr-Mo steels. In the second chapter, we present a thick interface model aiming to predict the whole spectrum of conditions at an alpha/gamma interface during ferrite growth, from full equilibrium to paraequilibrium with intermediate cases as the most interesting feature. The model, despite its numerous simplifying assumptions to facilitate its numerical implementation, allows to predict some peculiar kinetics in Fe-C-X systems with a minimum of fitting parameters, mainly the ratio between the diffusivities of the substitutional element inside the thick interface and in bulk austenite. The third chapter deals with the phase field model of austenite to ferrite transformation in steels. A thorough analysis on the conditions at the interface has been performed using the technique of matched asymptotic expansions. Special attention is given to clarify the role of the interface mobility on the growth regimes both in simple Fe-C alloys and in more complex Fe-C-Mn alloys

Parmi les scénarios accidentels hypothétiques étudiés dans le cadre des études de sûreté des Réacteurs à Eau Pressurisée (REP), figure l’Accident par Perte de Réfrigérant Primaire (APRP). Dans ce scénario, les gaines en alliage de zirconium qui contiennent le combustible nucléaire sont soumises à une oxydation importante à haute température (T≈ 1200 °C) dans de la vapeur d’eau. Les gaines étant la première barrière de confinement des radioéléments, il est primordial qu’elles conservent une certaine ductilité résiduelle après la trempe pour conserver son intégrité. Cette propriété est directement liée aux cinétiques de croissance de la zircone et de la phase αZr(O), ainsi qu’au profil de diffusion de l’oxygène dans le métal au cours du régime transitoire. Dans ce cadre, la compréhension et la modélisation du phénomène d’oxydation et de diffusion de l’oxygène dans les alliages de zirconium à haute température ont fait l’objet de cette thèse. Le modèle cinétique (EKINOX-Zr), développé au cours de cette thèse, est basé sur la résolution numérique d’un problème de diffusion/réaction avec des conditions aux limites sur trois interfaces mobiles : gaz/oxyde, oxyde/αZr(O) et αZr(O)/βZr. Le couplage du code cinétique avec le logiciel ThermoCalc et la base de données thermodynamiques Zircobase permet de prendre en compte l’influence des éléments d’alliages (Sn, Fe, Cr, Nb) et de l’hydrogène. Cette étude s’est plus particulièrement intéressée à deux aspects de l’APRP : l’influence d’une couche de pré-oxyde (formée aux températures des conditions de service du réacteur) et les effets de l’hydrogène. Grâce au couplage avec la base thermodynamique Zircobase, l’effet de l’hydrogène sur les limites de solubilité de l’oxygène dans les différentes phases a pu être pris en compte dans le modèle cinétique. Les simulations ont ainsi permis de reproduire les profils de concentration en oxygène mesurés sur différents échantillons pré- hydrurés. Par ailleurs, l’existence de couche de pré-oxyde de forte épaisseur peut conduire à une réduction transitoire de la couche de pré-oxyde dans les premiers instants du palier à haute température sous vapeur d’eau, avant formation de l’oxyde haute température. Une première série de simulations à l’aide du modèle cinétique EKINOX-Zr a permis de reproduire qualitativement ce chemin cinétique et a montré que cette couche formée à basse température possède des propriétés de diffusion particulières. Des expériences de traceurs sous 16O2/18O2 ont été réalisées sur des gaines pré-oxydées en autoclave pour étudier la diffusion de l’oxygène à haute température dans ces couches formées à basse température. D’autre part, le modèle cinétique EKINOX-Zr a été modifié pour prendre en compte la diffusion des traceurs. La confrontation des expériences avec les calculs a permis d’étudier les propriétés de diffusion particulières de la couche d’oxyde basse-température ainsi qu’une évolution des propriétés de diffusion de la phase αZr(O) formée par dissolution de l’oxyde à haute température. / One of the hypothetical accident studied in the field of the safety studies of Pressurized light Water Reactor (PWR) is the Loss-Of-Coolant-Accident (LOCA). In this scenario, zirconium alloy fuel claddings could undergo an important oxidation at high temperature (T≈ 1200 °C) in a steam environment. Cladding tubes constitute the first confinement barrier of radioelements and then it is essential that they keep a certain level of ductility after quenching to ensure their integrity. These properties are directly related to the growth kinetics of both the oxide and the αZr(O) phase and also to the oxygen diffusion profile in the cladding tube after the transient. In this context, this work was dedicated to the understanding and the modeling of the both oxidation phenomenon and oxygen diffusion in zirconium based alloys at high temperature. The numerical tool (EKINOX-Zr) used in this thesis is based on a numerical resolution of a diffusion/reaction problem with equilibrium-conditions on three moving boundaries : gas/oxide, oxide/αZr(O), αZr(O)/ βZr. EKINOX-Zr kinetics model is coupled with ThermoCalc software and the Zircobase database to take into account the influence of the alloying elements (Sn, Fe, Cr, Nb) but also the influence of hydrogen on the solubility of oxygen. This study focused on two parts of the LOCA scenario : the influence of a pre-oxide layer (formed in-service) and the effects of hydrogen. Thanks to the link between EKINOX-Zr and the thermodynamic database Zircobase, the hydrogen effects on oxygen solubility limit could be considered in the numerical simulations. Thus, simulations could reproduce the oxygen diffusion profiles measured in pre-hydrided samples. The existence of a thick pre-oxide layer on cladding tubes can induce a reduction of this pre-oxide layer before the growth of a high-temperature one during the high temperature dwell under steam. The first simulations performed using the numerical tool EKINOX-Zr showed that this particular kinetics pathway was qualitatively well reproduced by the modeling. It was also showed that the pre-oxide layer (formed at low-temperature) has particular diffusion properties. Consequently, some 18O tracer experiments were performed on pre-oxidized cladding tubes (pre-oxidizing done in autoclave) in order to study the diffusion properties of this oxide layers formed at low-temperature. Furthermore, EKINOX-Zr was modified to take into account the diffusion of tracer species. Both the diffusion properties of the low-temperature oxide layer and the evolution of the diffusion properties of the αZr(O) phase (formed by reduction of the oxide layer) were studied by comparing experiments and numerical simulations.

La prédiction des microstructures représente un enjeu majeur pour l'étude des processus de vieillissement des alliages métalliques, en particulier sous irradiation. Les résultats des calculs ab initio de structure électronique peuvent être utilisés pour paramétrer les méthodes cinétiques de Monte Carlo Atomique et permettent ainsi de simuler quantitativement la diffusion des atomes et l'évolution de la microstructure qui en résulte. Cette méthode est cependant limitée par le temps de calcul qu'elle exige. Les simulations mésoscopiques évitent cet écueil, mais souffrent généralement de ne pouvoir être paramétrées sur les résultats obtenus aux échelles inférieures, limitant ainsi leur pouvoir de prédiction. Dans ce travail, une méthode de simulation appelée Monte Carlo cellulaire cinétique a été développée pour relier les échelles atomiques et mésoscopiques tout en conservant la nature discrète des atomes. Une procédure de paramétrisation basée sur les simulations Monte Carlo à l'échelle atomique a été établie. Elle permet de reproduire quantitativement les propriétés macroscopiques d'équilibre des alliages indépendamment de la taille des cellules utilisées. Une application à l'alliage fer-cuivre est présentée. Afin de décrire les propriétés cinétiques à ces échelles, un outil générique de calcul de la matrice d'Onsager dans les alliages a été mis en place. Il est fondé sur la theorie du Champ Moyen Auto-Cohérent. Les résultats obtenus sur des cinétiques de diffusion et de précipitation dans un alliage modèle sont présentés et validés par une comparaison systématique avec des simulations Monte Carlo à l'échelle atomique. / Predicting microstructural evolution is a decisive step in the study of aging processes in alloys, especially under irradiation. The results of ab initio calculations of electronic structures can be used to parameterize kinetic methods such as Atomic Kinetic Monte Carlo simulations that allow reproducing quantitatively atomic diffusion and the resulting microstructure. Their use is however limited by their computational cost. Mesoscopic simulations are less concerned by such limitation, but suffer from the lack of reliable parameterization method to use data from simulations at lower scales that leads to a limited prediction capacity. A simulation method called Cellular Kinetic Monte Carlo is developed in this work to bridge the gap scales between atomic and mesoscopic scale simulation of diffusion. A crystal is there modeled as a. This method is based on a description of the crystal as a lattice of cells described by the discrete number of solute atoms they represents. The properties are then obtained by a controlled coarse-graining procedure based on Atomic Kinetic Monte Carlo simulations. It allows reproducing quantitatively macroscopic equilibrium for all cell sizes and has been applied to the Iron-Copper alloy. In order to describe kinetic properties at these scales, a generic computational tool has been developed to compute the Onsager matrix of alloys, based on the Self Consistent Mean field method. Diffusion and precipitation simulations have been done and the results are presented and assessed by a systematic comparison with Atomic Kinetic Monte Carlo simulations.

O presente trabalho teve como objetivo o estudo do estado sólido do ganciclovir (GCV) e suas diferentes formas polimórficas. O GCV é um fármaco antiviral útil no tratamento de infecções por citomegalovírus (CMV). Embora seja um fármaco amplamente usado, poucos estudos têm sido realizados sobre seu estado sólido. Atualmente, o GCV é conhecido por apresentar quatro formas cristalinas, duas anidras (Forma I e II) e duas hidratas (III e IV). Neste trabalho, nós reportamos a solução da estrutura cristalográfica da Forma I do GCV, que foi encontrado durante o screening de cristalização do fármaco, em que nove ensaios de cristalização (GCV-1, GCV-A, GCV-B, GCV-C, GCV-D, GCV-E, GCV-F, GCV-G e GCV-H) foram realizados e os materiais resultantes foram caracterizados por Difratometria de raios X (DRX), análise térmica (DTA/TG) e Hot Stage Microscopy. De todas as cristalizações realizadas foram obtidas quatro formas sólidas, denominadas como Forma I (GCV-1, GCV-B e GCV-H), Forma III (GCV-C, GCV-D, GCV-F e GCV-G), Forma IV (GCV-A) e Forma V (GCV-E). Esta última está sendo descrita pela primeira vez na literatura e indica a presença de outra forma hidratada de GCV. As Formas I, III e IV corresponderam a forma anidra e as duas formas hidratadas do fármaco, respectivamente. Além disso, foi evidenciado por experimentos de conversão de slurry e análise térmica que o cristalizado de GCV-1 (Forma I) foi o mais estável entre os materiais obtidos, e este deu origem ao monocristal da Forma I de GCV, estrutura cristalina anidra do fármaco. Neste trabalho, pela primeira vez, a estrutura cristalina deste composto foi definida por cristalografia de raios X de monocristal. A análise estrutural mostrou que a Forma I do fármaco cristaliza no grupo espacial monoclínico P21/c e está composta por quatro moléculas de GCV na sua unidade assimétrica. Cada molécula está unida intermolecularmente por ligações de hidrogênio, que dão lugar à formação de cadeias infinitas e estas por sua vez se arranjam de maneira a formar uma estrutura tridimensional. / This presented work aims to study the solid state of ganciclovir (GCV) and its different polymorphic forms. GCV is an antiviral drug useful in the treatment of cytomegalovirus (CMV) infections. Although it is a widely-used drug, few studies have been conducted on its solid state. Currently, GCV is known to have four crystalline forms, two anhydrous (Form I and II) and two hydrates (III and IV). In this investigation, we report a successful preparation of GCV Form I and its crystallographic structure, which was found during the crystallization of the drug, in which nine crystallization tests (GCV-1, GCV-A, GCV-B, GCV- D, GCV-E, GCV-F, GCV-G and GCV-H) were performed and the resulting materials were characterized by X-ray diffractometry (XRD), thermal analysis (DTA/TG) and Hot Stage Microscopy. Of all the crystallizations performed, four solid forms were obtained, denoted as Form I (GCV-1, GCV-B and GCV- H), Form III (GCV-C, GCV-D, GCV-F and GCV-G), Form IV (GCV-A) and Form V (GCV-E). The latter is being described for the first time in the literature and indicates the presence of another hydrated form of GCV. Forms I, III and IV corresponded to the anhydrous form and the two hydrated forms of the drug, respectively. In addition, it was evident by both the slurry conversion and the thermal analysis methods that the GCV-1 crystallized (Form I) was indeed the most stable amongst the materials obtained. This gave rise to GCV Form I monocrystal, anhydrous crystalline structure of the drug. The compound was characterized by monocrystal X-ray crystallography. The structural analysis showed that Form I of the drug crystallized in the monoclinic system space group P21/c is composed of four molecules of GCV in its asymmetric unit. Each molecule is linked intermolecularly by hydrogen bonds, which give rise to the formation of infinite chains arranged in a way that form a three-dimensional structure.

Owing to the growing demand for enantiopurity in biological and chemical processes, tremendous efforts have been devoted to the synthesis of homochiral metal-organic materials (MOMs) because of their potential applications in chiral separation and asymmetric catalysis. In this dissertation, the synthetic strategies for homochiral MOMs are discussed keeping the focus on their applications. Two distinct approaches have been taken to synthesize chiral structures with different topologies and accessible cavities. The chiral MOMs have been utilized in enantioselective separation of racemates. Chiral variants of the prototypal metal-organic framework MOF-5, δ-CMOF-5 and [lambda]-CMOF-5, have been synthesized by preparing MOF-5 in the presence of L-proline or D-proline, respectively. CMOF-5 crystallizes in chiral space group P213 instead of Fm-3m as exhibited by MOF-5. The phase purity of CMOF-5 was validated by single crystal and powder X-ray diffraction, IR spectroscopy, TGA, N2 adsorption, microanalysis and solid-state CD. CMOF-5 undergoes a reversible single crystal to single crystal phase change to MOF-5 when immersed in a variety of organic solvents although N-methyl-2-pyrolidone, NMP, does not induce loss of chirality. Indeed, MOF-5 undergoes chiral induction when immersed in NMP, affording racemic CMOF-5. A pair of homochiral network materials (CNMs), [Co2(S-man)2(bpy)3](NO3)2·guests (1S) and [Co2(R-man)2(bpy)3](NO3)2·guests (1R) based upon S-mendelic acid and R-mendelic acid were synthesized and characterized, respectively. The cationic networks contain 1D homochiral channels with the cross section of 8.0 Å × 8.0 Å. The chiral amphiphilic channel surfaces lined with hydrophilic nitrate anions and hydrophobic phenyl groups are capable for multiple interactions with guest species. Chiral resolution of 1-phenyl-1-propanol (PP) enantiomers was performed utilizing the homochiral porosity of 1S and 1R through different time period at different temperatures with/without additives. The mechanism for enantioselective separation of PP was fully investigated through single crystal structural analysis of guest exchanged 1S and 1R. Chiral resolution of PP revealed enhanced performance with additive, which can significantly improve the ee value from 32% to 60%.

<p>Understanding lithium-ion insertion/extraction mechanisms in battery electrode materials is of crucial importance in developing new materials with better cycling performance. In this thesis, these mechanisms are probed for two different potential cathode materials by a combination of electrochemical and single-crystal X-ray diffraction studies. The materials investigated are V₆O₁₃and cubic LiMn₂O₄spinel.</p><p>Single-crystal X-ray diffraction studies of lithiated phases in the Li_xV₆O₁₃ system (x=2/3 and 1) exhibit superlattice phenomena and an underlying Li⁺ ion insertion mechanism which involves the stepwise addition of Li⁺ions into a two-dimensional array of chemically equivalent sites. Each successive stage in the insertion process is accompanied by a rearrangement of the Li⁺ ions together with an electron redistribution associated with the reduction of specific V-atoms in the structure. This results in the formation of electrochemically active sheets in the structure. A similar mechanism occurs in the LiMn₂O₄ delithiation process, whereby lithium is extracted in a layered arrangement, with the Mn atoms forming charge-ordered Mn³⁺/Mn⁴⁺ layers.</p><p>Lithium-ion insertion/extraction processes in transition-metal oxides would thus seem to occur through an ordered two-dimensional arrangement of lithium ions extending throughout the structure. The lithium ions and the host structure rearrange cooperatively to form superlattices through lithium and transition-metal ion charge-ordering. A picture begins to emerge of a universal two-dimensional lithium-ion insertion/extraction mechanism analogous to the familiar staging sequence in graphite.</p>