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The creation of new materials is absolutely essential for developing new technologies. However, experimental efforts toward the material discovery are usually based on trial-and-error approach and thus require a huge amount of time and money. Alternatively, computational predictions can now provide a more systematic, rapid, inexpensive, and reliable method for the design of novel materials with properties suitable for new technologies. This dissertation describes the technique of theoretical predictions and presents the results on the successfully predicted and already produced (in some cases) unusual molecules, clusters, nanoparticles, and solids. The major part of scientific efforts in this dissertation was devoted to rationalizing of size- and composition-dependent properties of the materials based on understanding of their electronic structure and chemical bonding. It was shown that understanding relations between bonding and geometric structure, bonding and stability, and bonding and reactivity is an important step toward rational design of new, yet unknown materials with unusual properties. Our findings led to the discovery of the first simplest inorganic double helix structures, which can be used in the design of novel molecular devices. A significant part of this work also deals with the pseudo John-Teller effect, which potentially can be a powerful tool for rationalizing and predicting molecular and solid state structures, their deformations, transformations, and properties. Therefore, the works on the pseudo Jahn-Teller effect presented in this dissertation can be considered the steps toward further generalization and elevation of the pseudo Jahn-Teller effect to a higher level of understanding of the origin of molecular and solid state properties.

This thesis primarily focuses on the systematic understanding of structure – reactivity relationships in two representative systems: bixbyite and related structures as well as indium doped CeO2. Topotactic reaction routes have gained significant attention over the past two decades due to their potential to access kinetically controlled metastable materials. This has contributed substantially to the understanding of solid state reaction pathways and provided first insights into mechanisms. Contrary to the widely used ex-situ methods, in – situ techniques including powder x-ray diffraction and thermogravimetric – differential thermal analysis have been employed extensively throughout this work in order to follow the reaction pathways in real time. Detailed analysis of the AVO3 (A = In, Sc) bixbyite reactivity under oxidative conditions has been carried out and a variety of novel metastable oxygen defect phases have been identified and characterized. The novel metastable materials have oxygen deficient fluorite structures and consequently are potential ion conductors. Structural aspects of the topotactic vs. reconstructive transformations are illustrated with this model system. The structure – reactivity study of AVO3 phases was extended to AVO3 perovskite family. Based on the research methodologies and results from AVO3 bixbyite reactivity studies a generalized mechanistic oxidation pathway has been established with a non-vanadium phase, ScTiO3 bixbyite. However, there is stark contrast in terms of structural stability and features beyond this stability limit during AVO3 and ScTiO3 bixbyite reaction pathways. A series of complex reaction sequences including phase separation and phase transitions were identified during the investigation of ScTiO3 reactivity. The two-step formation pathway for the fluorite – type oxide ion conductor Ce1-xInxO2-δ (0 ≤ x ≤ 0.3) is being reported. The formation of the BaCe1-xInxO3-δ perovskites and the subsequent CO2-capture reaction with the formation of Ce1-xInxO2-δ (0 ≤ x ≤ 0.3) has been investigated in detail. The two-step formation pathway is contrasted with the unsuccessful direct method. The stability and the extent of In – doping for the CeO2 fluorite phases that can be achieved through this CO2 – capture method are reported. The necessity and strategies for the selection of appropriate intermediate precursors for the preparation of doped CeO2 are also reported.

Orientador: Prof. Dr. Jorge Tomioka / Dissertação (mestrado) - Universidade Federal do ABC, Programa de Pós-Graduação em Engenharia Elétrica, 2014. / Este trabalho apresenta um estudo para a área de iluminação residencial, por meio da utilização da tecnologia de iluminação do estado sólido LED (diodos emissores de luz). Seu objetivo principal é apresentar a economia de energia elétrica para o país trazendo soluções mais eficientes para nossas residências, inclusive podendo ser estendido a outros setores, como indústria e comércio. Isso gerará economia de energia elétrica para o País e favorecerá a preservação do meio ambiente, com a diminuição da emissão de dióxido de carbono (CO2), produzindo impacto imediato na utilização de energia elétrica e prorrogando os grandes investimentos em geração de energia elétrica no Brasil, fazendo reduzir os gastos do dinheiro público. Para a pesquisa, foram levantados vários conceitos aplicados a luminotécnica, para um maior aprofundamento e consolidação dos resultados. Após a fase de pesquisa dos conceitos, foram estudadas as características das diferentes tecnologias de lâmpadas de uso residencial. Foi montada uma bancada para os ensaios das amostras, facilitando a realização das medições, o levantamento de algumas características técnicas, tais como potência da lâmpada, fator de potência, fluxo luminoso e eficiência luminosa. Com a estratificação desses resultados, foi elaborado um estudo de viabilidade econômica entre as três tecnologias de lâmpadas, mostrando o tempo de retorno do investimento. Em seguida, foram realizadas simulações entre as tecnologias de lâmpadas com projeção do consumo de energia elétrica para o ano de 2021. Com a realização deste trabalho cientifico, foi possível chegar a conclusões fundamentais acerca da melhor tecnologia de lâmpada que pode ser aplicada no País no setor residencial. / This work presents a study for the residential lighting through the use of solid-state lighting technology LED ( light emitting diodes ). Its main purpose is to present the economics of electricity for the country bringing more efficient solutions for our homes, and may even be extended to other sectors such as industry and commerce. This will generate electricity savings for the country and encourage the preservation of the environment, with the reduction in the emission of carbon dioxide (CO2), producing immediate impact on electricity usage and extending large investments in power generation in Brazil doing reduce spending of public money . For the research, various concepts applied to illumination, for further development and consolidation of results were collected. After the research phase of the concepts, characteristics of different technologies lamps residential use were studied. A workbench was assembled for testing the samples, facilitating the measurements, raising some technical features, such as the lamp power, power factor, luminous flux and luminous efficiency. Stratification with these results, an economic feasibility study between the three technologies lamps was prepared, showing the time of investment return. Then simulations between technologies of projection lamps with electricity consumption for the year 2021 were performed. With the completion of this scientific work, it was possible to reach basic conclusions about the best lamp technology that can be applied in the Country residential sector.

The thesis entitled “Local structure-property relationship in some selected Solid State Materials” mainly focuses on two fundamental topics: (a) evaluation of some standard global structural concepts in terms of local structure to provide a unique description of the crystal structure, and (b) the role of the crystal structure at different length-scales in controlling the properties in some selected materials.