Desde a identificação do vírus da imunodeficiência humana (HIV, do inglês Human Immunodeficiency Virus) como agente causador da Síndrome da Imunodeficiência Adquirida (AIDS ? do inglês Acquired Immunodeficiency Syndrome), a busca para tratamentos seguros e eficazes contra o HIV transformou-se no principal foco para a descoberta de uma nova droga em todo o mundo. A AIDS aparece como um dos principais problemas de saúde pública para as próximas décadas, onde será o maior determinante de mortalidade na faixa etária entre 20 e 50 anos em praticamente todos os países do mundo. Tendo como objetivo relacionar a atividade de compostos biflavonóides anti-HIV-1 com algumas de suas propriedades moleculares, serão utilizados métodos de Mecânica Molecular e Química Quântica. O método de cálculo semi-empírico AM1 foi empregado para calcular um conjunto de propriedades moleculares dos 14 compostos biflavonóides com atividade anti-HIV-1. A seguir utilizar-se-á métodos estatísticos com a finalidade de separar os 14 compostos em duas classes, ativos e não ativos, de forma que se relacione qual as propriedades, dentre as calculadas, são responsáveis pela atividade dos compostos biflavonóides estudados. As técnicas estatísticas utilizadas foram a Análise de Componentes Principais (PCA: Principal Components Analysis), Análise Hierárquica de Agrupamentos (HCA: Hierarquical Clusters Analysis) e Análise de Discriminates por Passos (SDA: Stepwise Discriminant Analysis). Os estudos com PCA, HCA, e SDA mostraram que as variáveis HOMO (Highest Occupied Molecular Orbital - Orbital Molecular Ocupado de Maior Energia), LUMO (Lowest Unoccupied Molecular Orbital ? Orbital Molecular Desocupado de Menor Energia), e Área superficial são responsáveis pela separação dos compostos com alta e baixa atividade anti-HIV-1. O comportamento destas três propriedades pode ser útil na tentativa de se obter outros compostos biflavonóides com elevada atividade inibidora anti-HIV-1. / A set of 25 quinone compounds with anti-trypanocidal activity was studied by using the Density Functional Theory (DFT) method in order to calculate electronic atomic and molecular properties to be correlated with the biological activity. The chemometric methods Principal Component Analysis (PCA), Hierarchical Cluster Analysis (HCA), Stepwise Discriminant Analysis (SDA), Kth nearest neighbor (KNN) and Soft Independent Modeling of Class Analogy (SIMCA) were used to obtain possible relationships between the calculated descriptors and the biological activity studied and predict the anti-trypanocidal activity of new quinone compounds from a test set. Four descriptors were responsible for the separation between the active and inactive compounds: T5 (torsion angle), HOMO-1 (energy of the first molecular orbital below HOMO), QTS1 (sum of absolute values of the atomic charges) and VOLS2 (volume of the substituent at region B). These descriptors give information on the kind of interaction that occurs between the compounds and the biological receptor. The prediction study was done with a set of three new quinone compounds by using the PCA, HCA, SDA, KNN and SIMCA. Beside the five chemometric methods, the neural network method was used by employing the backpropagation algorithm. The four variables (T5, QTS1, VOLS2 and HOMO-1) were employed to validate the models constructed previously. The architecture of networks consisting of four neurons at input layers, ten neurons at intermediary layers and two neurons at output layers was adopted to observe the root mean square error between the true and desired output over the entire training set. The percentage of correct classification was 87.5%, and only one compound was predicted wrong in the test set, which indicates that the model is robust and could be able to make predictions. The docking studies were carried out with two different programs in the approach of ligands: the Autodock and FlexX. The docking results on trypanothione reductase enzyme showed that all studied compounds stay at second hydrophobic pocket in the outer region of the active site called the Z-site. The residues that could be specifically involved in the binding of ligands are Lys62, Thr66, Thr397, Thr463, Leu399, Ser464, Glu466 and Glu467, where the residues Thr66, Thr463 and Leu399 are conserved in different trypanothiones and could be used for the development of selective inhibitors against to the parasite enzyme.

Nanoclusters de metais de transição (TM) com dimensões de &#126;1,0 nm têm atraído grande interesse em diversas aplicações tecnológicas, como microeletrônica, óptica, dispositivos magnéticos e principalmente como nanocatalisadores. Nesse contexto, a morfologia desses sistemas é um fator fundamental para otimzação de performace nessas aplicações, tendo em vista a relação direta entre as propriedades físico-químicas e a estrutura atômica do nanocluster determinada pelas condições do ambiente (temperatura e moléculas adsorvidas). No entanto, diante das limitações relativas à precisão das técnicas de caracterização experimental disponíveis atualmente, sobretudo em dimensões nanométricas, o uso de cálculos computacionais através de métodos de primeiros princípios (ab initio) e baseados na teoria do funcional da densidade se torna indispensável. Neste trabalho, foram investigados os efeitos de ligantes e temperaturas nas propriedades estruturais, eletrônicas, estabilidade e meta-estabilidade de nanoclusters de TM. (i) Os efeitos de ligantes de (PH3)n e (SH2)n (saturação gradativa em n = 1, 6, 12 e 18) adsorvidos em nanoclusters unários de Pt55 e Au55 com estruturas icosaédricas (ICO), cuboctaédricas (CUB) e desordenadas de core reduzido (DRC) foram estudados a 0K. Em fase gasosa, as estruturas DRC com 7 e 9 átomos na região do core são 5,34 eV (Pt55) e 2,20 eV (Au55) mais estáveis que modelo ICO com simetria Ih com 13 átomos no core. Os resultados mostraram que existe uma forte compressão do core catiônico pela superfície aniônica induzida por interações de Coulomb (core+-superfície-), levando ao colapso e redução de estresse das estruturas simétricas a partir da redução do número de átomos na região do core. No entanto, a estabilidade da estrutura ICO aumenta com o aumento do número de moléculas adsorvidas, de modo que DRC e ICO se tornam energeticamente degeneradas em < 0,5 eV. Além disso, a adição de ligantes na superfície aniônica reduz a transferência de cargas entre as regiões de core+-superfície-, contribuindo para a redução das interações de Coulomb e, consequentemente, aliviando o estresse interno da estrutura ICO. Resultados similares foram obtidos utilizando ligantes de trifenilfosfina (PPh3), nos quais as longas cadeias carbônicas adicionam interações laterais entre os ligantes. (ii) Nanoclusters de binários de PtnCo(55 - n) a 0K mostraram alta estabilidade em todo intervalo de composições, indicando uma correlação direta entre estabilidade e distribuição homogênea de átomos de Pt e Co formando a nanoliga com estrutura ICO. No entanto, sob uma atmosfera saturada de ligantes de CO adsorvidos, a estabilidade da nanoliga diminui (aumenta) para composições com grandes quantidades de Pt (Co). As análises mostraram que sob os efeitos da adsorção as composições permanecem com configuração ICO, exceto para Pt42Co13 (estrutura core@shell do tipo Co@Pt em fase gasosa), onde as moléculas de CO deslocam os átomos de Co para a superfície, e, então, induzindo um processo de amorfização na formação de uma estrutura formada com átomos de Pt ocupando o core. Para investigar os efeitos de temperatura na estabilidade e meta-estabilidade de nanoclusters e clusters de Au utilizando dinâmica molecular de Born-Oppenheimer, foram utilizados nanoclusters de tamanho médio de Au25, Au38 e Au40 em fase gasosa e clusters de Au13 sob diferentes atmosferas saturadas de CO. (iii) Observou-se que em temperaturas de 300, 400, 500 e 600 K os nanoclusters exibem estruturas dinâmicas para as regiões de core-superfície, com core tetraédrico (4 átomos) ou T-bipiramidal (5 átomos) catiônicos fracamente ligados à superfície aniônica flexível. Uma abordagem estatística através de um algoritmo de redução de dimensionalidades para representação no espaço euclideano bidimensional, chamado de sketch-map, foi proposta como uma nova linguagem para analisar a superfície de energia livre (FES) dos sistemas calculada na aproximação de multistate Bennet acceptance-ratio. A FES foi utilizada como uma análise qualitativa das configurações estáveis e meta-estáveis sob os efeitos de temperaturas, indicando as regiões preferenciais do espaço configuracional de cada nanocluster investigado. (iv) Incluindo os efeitos de ligantes e temperaturas em clusters de Au13, foi observado que em altas temperaturas os clusters de Au13 em fase gasosa tendem a configurações mais abertas com menor comprimento de ligação com relação às estruturas tridimensionais. Por outro lado, a saturação do ambiente com ligantes de CO restringem a mobilidade dos átomos nos clusters de Au13, favorecendo a amostragem de estruturas tridimensionais mesmo em temperaturas relativamente altas. A análise de população de cargas mostrou uma alta concentração de elétrons nos átomos de O, de modo que o forte catiônico dos clusters de Au13 leva ao aumento da coordenação atômica, contribuindo para a estabilização das estruturas mais tridimensionais. / Transition metal nanoclusters (TM) with dimensions of &#126;1,0 nm have attracted great interest in various technological applications such as microelectronics, optics, magnetic devices and mainly as nanocatalysts. In this way, the morphology of these systems is a fundamental factor for optimization of performance in these applications, considering the direct relationship between the physicochemical properties and the atomic structure of the nanocluster determined by the ambient conditions (temperature and adsorbed molecules). In this sense, in view of the limitations on the precision of the experimental characterization techniques currently available, especially in nanometric dimensions, the use of computational calculations using first principles methods (ab initio) and based on the density functional theory is indispensable. Thus, in this work, the effects of binders and temperatures on the structural, electronic properties, stability and metastability of TM nanoclusters were investigated. (i) In this way, the (PH3)n and (SH2)n ligands effects with gradual saturation at n = 1, 6, 12 and 18 adsorbed onto nanoclusters Pt55 and Au55 with icosahedral (ICO), cuboctahedron (CUB), and distorted reduced core (DRC) structures were studied at 0K. In the gas phase, the DRC structures with 7 and 9 atoms in the core region are 5,34 eV (Pt55) and 2,20 eV (Au55) more stable than ICO model with symmetry Ih with 13 atoms in core. The results showed that there is a strong compression of the cationic core by the anionic surface induced by interactions of Coulomb (core+-surface-), leading to collapse and stress reduction of the symmetrical structures from the reduction of the number of atoms in the core region. However, the stability of the ICO structure increases with increasing Number of molecules adsorbed, so that DRC and ICO become approximately degenerated in energy in < 0,5 eV. In addition, ligands on the anionic surface reduces the transfer of charges between core+- surface-, contributing to the reduction of interactions of Coulomb and, consequently, alleviating the internal stress of the ICO. Similar result were obtained using triphenylphosphine (PPh3) as large ligands, in which the long carbon chains add side interactions between the ligands. (ii) PtnCo(55 - n) binares nanoclusters at 0K showed a high stability across the range of compositions, indicating a direct correlation between stability and homogeneous distribution of Pt and Co atoms forming the nanoalloys with ICO structure. However, under a saturated atmosphere of adsorbed CO ligands, the stability of the nanoaaloys decreases (increases) to compositions with large amounts of Pt (Co). Analyzes have shown that under the effects of adsorption the compositions remain with ICO configuration, except for Pt42Co13 (Co@Pt as core@shell in gas-phase), where Co molecules displace the Co atoms to the surface, and then inducing an amorphization process for a structure formed with Pt atoms occupying the core. To investigate the temperature effects on the stability and metastability of Au nanoclusters and clusters by using Born-Oppenheimer molecular dynamics, medium size nanoclusters of Au25, Au38, and Au40 were used in gas-phase and clusters of Au13 under different saturated atmospheres of CO. (iii) It has been observed that at temperatures of 300, 400, 500, and 600 K, the nanoclusters exhibit dynamic structures for the core-surface regions with cationic tetrahedral (4 atoms) or T-bipyramidal (5 atoms) cores weakly bound to the flexible anionic surface. A statistical approach using a dimensionality reduction algorithm for two-dimensional Euclidean space representation, called sketch-map, was proposed as a new language to analyze the free energy surface (FES) of the systems calculated on the approximation of multistate Bennet acceptance-ratio. The FES was used as a qualitative analysis of the stable and metastable configurations under the effect of temperature, indicating the preferred regions of the configurational space of each nanocluster investigated. (iv) By including the effects of ligands and temperatures on Au13 clusters, it was observed that at high temperatures the Au13 clusters in gas-phase tend to have more open configurations with less bond length relative to three-dimensional structures. On the other hand, the saturation of the environment with CO ligands restricts the mobility of the atoms in Au13 clusters, favoring the sampling of three-dimensional structures even at temperatures relatively high. The charge population analysis showed a high concentration of electrons in the O atoms, so that the strong cationic character of the Au13 clusters leads to increased atomic coordination, contributing to the stabilization of the more three-dimensional.

In the past decade the interest in molecular electronic devices has escalated. The synthesis of molecular crystals has improved, providing single crystals or thin films with mobility comparable with or even higher than amorphous silicon. Their mechanical flexibility admits new types of applications and usage of electronic devices. Some of these organic crystals also display magnetic effects. Furthermore, the fullerene and carbon nanotube allotropes of carbon are prominent candidates for various types of applications. The carbon nanotubes, in particular, are suitable for molecular wire applications with their robust, hollow and almost one-dimensional structure and diverse band structure. In this thesis, we have theoretically investigated carbon based materials, such as carbon nanotubes, pentacene and spiro-biphenalenyl neutral radical molecular crystals. The work mainly deals with the electron structure and the transport properties thereof. The first studies concerns effects and defects in devices of finite carbon nanotubes. The transport properties, that is, conductance, are calculated with the Landauer approach. The device setup contains two metallic leads attached to the carbon nanotubes. Structural defects as vacancies and bending are considered for single-walled carbon nanotubes. For the multi-walled carbon nanotubes the focus is on inter-shell interaction and telescopic junctions. The current voltage characteristics of these systems show clear marks of quantum dot behaviour. The influence of defects as vacancies and geometrical deformations are significant for infinite systems, but in these devices they play a minor role. The rest of the studies concern molecular crystals, treated with density-functional theory (DFT). Inspired by the enhance of the electrical conductivity obtained experimentally by doping similar materials with alkali metals, calculations were performed on bundles of single-walled carbon nanotubes and pentacene crystals doped with potassium. The most prominent effect of the potassium intercalation is the shift of Fermi level in the nanotube bands. A sign of charge transfer of the valence electrons of the potassium atoms. Semi-conducting bundles become metallic and metallic bundles gain density of states at the Fermi level. In the semi-conducting pristine pentacene crystals structural transitions occur upon doping. The herringbone arrangement of the pristine pentacene molecules relaxes to a more π-stacked structure causing more dispersive bands. The charge transfer shifts the Fermi level into the lowest unoccupied molecular orbital band and turns the crystal metallic. Finally, we have studied molecular crystals of spiro-biphenalenyl neutral radicals. According to experimental studies, some of these materials show simultaneous electrical, optical and magnetical bistability. The electronic properties of these crystals are investigated by means of DFT with a focus on the possible intermolecular interactions of radical spins.

Le but de cette thèse est de décrire l'impact des fluctuations thermiques quantiques sur les spectres XANES et RMN du solide, à l'aide d'une étude conjointe expérimentale et théorique. Ce projet comporte deux volets. D'une part, il s'agit d'acquérir des données expérimentales de très bonne qualité, afin d'observer et comprendre l'influence des vibrations quantiques dans les oxydes d'éléments légers. D'autre part, un modèle théorique est mis en place afin de reproduire les effets observés expérimentalement et décrire leur origine d'un point de vue fondamental. L'approche théorique développée est fondée sur la théorie de la fonctionnelle de la densité. Dans le cadre de l'approximation de Born-Oppenheimer et de l'approximation quasi-harmonique, les fluctuations thermiques de nature quantiques sont modélisées en générant des configurations atomiques obéissant à la statistique quantique à température finie. Les spectres XANES et paramètres RMN sont, par la suite, calculés dans ces configurations et les résultats moyens sont comparés aux données spectroscopiques à température finie. Cette approche a été validée par une étude menée dans une série d'oxydes d'éléments légers, où les résultats se sont avérés être en excellent accord avec les données expérimentales originales que nous avons enregistrées. En outre, il est montré que les fluctuations quantiques des noyaux ne jouent pas le même rôle selon la symétrie locale du site atomique sondé. / In this thesis the impact of quantum thermal fluctuations on XANES and solid-state NMR spectra is described using an experimental and theoretical joint study. This project has two components. First, high-quality experimental data are acquired in order to observe and understand the influence of quantum vibrations in light-elements oxides. Second, a theoretical model is set up to reproduce the effects observed experimentally and describe their origin from a fundamental point of view. The developed theoretical approach is based on the density-functional theory. Within the Born-Oppenheimer and quasiharmonic approximations, the quantum thermal fluctuations of nuclei are modeled by generating atomic configurations obeying quantum statistics at finite temperature. The XANES spectra and NMR parameters are subsequently calculated in these configurations and the average results are compared with spectroscopic data at finite temperature. This approach has been validated by a joint theoretical-experimental study conducted in a series of light-element oxides, where the results were found to be in excellent agreement with the original experimental data. In addition, it is shown that the impact of the quantum fluctuations of the nuclei is influenced by the local symmetry of the probed atomic site.

Doctor of Philosophy / Department of Chemical Engineering / Bin Liu / Efficient and selective catalysis lies at the heart of many chemical reactions, enabling the synthesis of chemicals and fuels with enormous societal and technological impact. A fundamental understanding of intrinsic catalyst properties for effective manipulation of the reactivity and selectivity of industrial catalysts is essential to select proper catalysts to catalyze the reactions we want and hinder the reactions we do not want. The progress in density functional theory (DFT) makes it possible to describe interfacial catalytic reactions and predict catalytic activities from one catalyst to another. In this study, water-gas shift reaction (WGSR) was used as a model reaction. First-principles based micro-kinetic modeling has been performed to deeply understand interactions between competing reaction mechanisms, and the relationship with various factors such as catalyst materials, structures, promoters, and interactions between intermediates (e.g., CO self-interaction) that govern the observed catalytic behaviors. Overall, in this thesis, all relevant reaction mechanisms in the model reaction on well-defined active sites were developed with first-principles calculations. With the established mechanism, the promotional effect of K adatom on Ni(111) on WGSR compared to the competing methanation was understood. Moreover, the WGSR kinetic trend, with the hydrogen production rate decreasing with increasing Ni particle diameters (due to the decreasing fractions of low-coordinated surface Ni site), was reproduced conveniently from micro-kinetic modeling techniques. Empirical correlations such as Brønsted-Evans-Polanyi (BEP) relationship for O-H, and C-O bond formation or cleavage on Ni(111), Ni(100), and Ni(211) were incorporated to accelerate computational analysis and generate trends on other transition metals (e.g., Cu, Au, Pt). To improve the numerical quality of micro-kinetic modeling, later interactions of main surface reaction intermediates were proven to be critical and incorporated successfully into the kinetic models. Finally, evidence of support playing a role in the enhancement of catalyst activity and the impact on future modeling will be discussed. DFT will be a powerful tool for understanding and even predicting catalyst performance and is shaping our approach to catalysis research. Such molecular-level information obtained from computational methods will undoubtedly guide the design of new catalyst materials with high precision.

Doctor of Philosophy / Department of Chemistry / Christine M. Aikens / Gold and silver particles with dimensions less than a nanometer possess unique characteristics and properties that are different from the properties of the bulk. They demonstrate a non–zero HOMO–LUMO gap that can reach up to 3.0 eV. These differences arise from size quantization effects in the metal core due to the small number of atoms. These nanoparticles have attracted great interest for decades both in fundamental and applied research. Small gold clusters protected by various types of ligands are of interest because ligands allow obtaining gold nanoclusters with given sizes, shapes and properties. Three main families of organic ligands are usually used for stabilization of gold nanoclusters: phosphine ligands, thiolate ligands and DNA. Usually, optical properties of these NPs are studied using optical absorption spectroscopy. Unfortunately, sometimes this type of spectrum is poorly resolved and tends to appear very similar for different complexes. In these cases, circular dichroism (CD) and magnetic circular dichroism (MCD) spectroscopy can be applied. However, the interpretation of experimental CD and MCD spectra is a complicated process. In this thesis, theoretically simulated CD and MCD spectra were combined with optical absorption spectra to study optical activity for octa– and nona– and undecanuclear gold clusters protected by mono– and bidentate phosphine ligands. Additionally, optical properties of bare and DNA protected silver NPs were studied. Theoretical CD spectra were examined to learn more about the origin of chirality in chiral organometallic complexes, and to contribute to the understanding of the difference in chiroptical activity of gold clusters stabilized by different phosphine ligands and DNA–stabilized silver clusters. Furthermore, optical properties of the small centered gold clusters Au₈(PPh₃)₈²⁺ and Au₉(PPh₃)₈³⁺ were examined by optical absorption and MCD spectra using TDDFT. Theoretical MCD spectra were also used to identify the plasmonic behavior of silver nanoparticles. These results showed that CD and MCD spectroscopy yield more detailed information about optical properties and electronic structure of the different chemical systems than optical absorption spectroscopy alone. Theoretical simulation of the CD and MCD spectra together with optical absorption spectra can be used to assist in the understanding of empirically measured CD and MCD and provide useful information about optical properties and electronic structure.

Kyoto University (京都大学) / 0048 / 新制・課程博士 / 博士(工学) / 甲第15612号 / 工博第3301号 / 新制||工||1498(附属図書館) / 28139 / 京都大学大学院工学研究科電子工学専攻 / (主査)教授 木本 恒暢, 教授 藤田 静雄, 准教授 山田 啓文 / 学位規則第4条第1項該当

Ces travaux de thèse se sont concentrés sur le développement, l'implémentation et l'application de différents types de méthodes quantiques prenant la corrélation électronique en compte, dans le but de fournir des outils performants pour la description de systèmes moléculaires à l'état fondamental et excité. La méthode dite DMRG (Density Matrix Renormalization Group) a été étudiée et un logiciel correspondant a été développé en FORTRAN. Cette méthode permet de limiter le nombre d'états électroniques à prendre en compte, ce qui fait gagner du temps de calcul, tout en assurant une précision des résultats du même ordre que celle fournie par les toutes meilleures méthodes post-Hartree-Fock actuelles. Dans la deuxième partie de cette thèse, nous avons utilisé une autre méthode : la DFT (Density Functional Theory). Une étude théorique a été effectuée sur deux fonctionnelles à séparation de portée (HISS-A et -B) afin d'évaluer dans quelle mesure ces fonctionnelles, développées au départ pour l'étude des systèmes métalliques, pouvaient être appliquées à la description de l'état fondamental et excité de systèmes moléculaires hautement conjugués. Nous avons également utilisé la DFT afin de modéliser et rationaliser le comportement photo-physique d'un composé moléculaire présentant une émission dite " duale ". Nous avons pu ainsi caractériser le comportement complexe de la molécule à l'état excité et expliquer les résultats surprenants qui avaient été observés, en particulier au niveau des spectres d'émission UV et d'excitation de fluorescence. Le phénomène d'émission duale observé a ainsi pu être lié à la présence d'un degré de liberté conformationnel important de la molécule. / In the last few years, a lot of energy has been put forward in the area of quantum chemistry to develop new methods, or to improve existing methods, that are able to describe very precisely the electronic structure of molecular systems. In this manuscript, a precise overview of such a method (namely the Density Matrix Renormalization Group, DMRG method) is given. A software able to carry out DMRG calculations has indeed been developed from scratch in the laboratory during this thesis. This method can be seen as a post-Hartree-Fock method, in which only the electronic states that are relevant for the correct description of the molecule are kept. In this way, the computational cost remains acceptable, and the results are in line with those given by "exact" methods such as full-CI. Density Functional Theory (DFT) has also been investigated in this work. DFT and TD-DFT calculations have indeed also been carried out. The performances of two middle-range-separated functionals, namely HISS-A and HISS-B, to describe electronic transitions in conjugated molecules have been probed in a theory vs. theory study. Those functionals, which had been first developed for the study of metals, show to be adequate for the correct description of electronic excitations of chromophores and of push-pull molecules. Optical properties of a dual emittor have also been studied using TD-DFT. The dual emission of this molecule has been shown to stem from the presence of two distinct emissive states, respectively of Intramolecular Charge Transfer (ICT) and locally excited (LE) nature. TD-DFT has allowed us to link those two emissive states to two different conformations of the molecule.

Abstract This thesis focuses on the molecular-level chemistry of the solvation of aluminum salts. Fundamental aspects such as, structural characteristics of the aluminum molecules, hydrolysis, acidity, solvation structure, effect of counter ions, and chemical stability are discussed herein. Static computations augmented with the conductor-like screening model (COSMO) were used to investigate hundreds of planar and cyclic configurations of dimeric, trimeric, tetrameric, and pentameric aluminum complexes. Car–Parrinello molecular dynamics (CPMD) calculations were used to expand investigations to aqueous environments. This thesis consists of four articles and one additional article. The first paper focuses on the structural analysis of the hydrolysis products of AlCl3 · 6H2O. Dimeric, trimeric, and tetrameric aluminum (chloro)hydroxides were investigated in both gas and liquid phase. The liquid environment was modeled by using COSMO. The second and the additional paper concentrate on the chemistry of aluminum sulfate complexes. The second article focuses on identifying hydrolysis products of AlCl3 · 6H2O in the presence of sulfate (H2SO4). The additional paper focuses on the structural characteristics of the hydrolysis products of Al2 (SO4)3 · 18H2O. Structural information was deduced from the ESI MS results with the aid of computational methods. Detected cationic structures closely resembled the aluminum chlorohydrate analogues introduced in the first paper. The third and fourth articles are devoted to the hydrolysis, stability, and dynamics of dimeric and pentameric aluminum (chloro)hydroxides in aquatic environments. During the CPMD simulations, several spontaneous associative hydration reactions were detected in the primary hydration shell of the complexes. Dimeric aluminum chlorohydrates were detected to be stable in liquid conditions, whereas the pentameric aluminum complexes experienced significant topological changes during the simulations. Constrained simulations were used to reveal the role of chloride ions in the hydrolysis processes of dimeric complexes. The effect of the empirical van der Waals corrections to the dynamics of the simulations was also tested for the pentameric system. The results of this thesis showed unequivocally that computational chemistry provides effective tools for structural analysis of inorganic complexes such as, aluminum chlorohydrates and sulfates in both gas and liquid phase. In addition, calculations provided answers to the anomalies detected in the experiments. Hence, theoretical methods are highly recommended to be used alongside with conventional experimental methods in the interpretation of the aluminum species in aqueous solutions and to widen the overall chemical perspective of the hydrolysis of aluminum salts.

As the foundation for a new computational implementation, we survey the calculation of the complex electrical conductivity tensor based on the Kubo-Greenwood (KG) formalism (Kubo, 1957; Greenwood, 1958), with emphasis on derivations and technical aspects pertinent to use of projector augmented wave datasets with plane wave basis sets (BIlichl, 1994). New analytical results and a full implementation of the KG approach in an open-source Fortran 90 post-processing code for use with Quantum Espresso (Giannozzi et al., 2009) are presented. Named KGEC ([K]ubo [G]reenwood [E]lectronic [C]onductivity), the code calculates the full complex conductivity tensor (not just the average trace). It supports use of either the original KG formula or the popular one approximated in terms of a Dirac delta function. It provides both Gaussian and Lorentzian representations of the Dirac delta function (though the Lorentzian is preferable on basic grounds). KGEC provides decomposition of the conductivity into intra- and inter band contributions as well as degenerate state contributions. It calculates the dc conductivity tensor directly. It is MPI parallelized over k-points, bands, and plane waves, with an option to recover the plane wave processes for their use in band parallelization as well. It is designed to provide rapid convergence with respect to k-point density. Examples of its use are given.