Doping and phase transitions processes on semiconductors and vibrational properties in complex glassesa theoretical and experimental investigation

Abstract

Technological advances have always accompanied the human progress and are largely driven by the design and discovery of new materials. Its impact on modern society plays a fundamental role in the strategies for the establishment of sustainable chemical technologies that are efficient from the energy point of view and respect the environment. Due to the rapid advancements in computing processors, computing hardware, and software, and in particular, the trade-off between accuracy and computational cost provided by the Density Functional Theory (DFT), the methods and techniques of the Theoretical and Computational Chemistry (TCC) not only play a central role in explaining, rationalizing, and predicting experimental results, but it has also increasingly become a valuable tool aimed at discovering and simulating new materials and catalysts. Modeling, at the atomic level, and the use of TCC calculations are a central aspect of modern chemistry and physics, providing a deeper insight into how advanced materials work. The design and synthesis processes for obtaining new materials can be accelerated using first principles calculations and it has rapidly evolved from an explanatory tool to support experimental characterization, allowing theory-driven design and optimization of materials to address some of the most pressing technological challenges of our time. Bridging the gap between experimental and computational researchers by fostering close collaborations is mandatory for making a breakthrough in the investigation of materials. The combined forces of these two pillars, experiment and in-depth computational analyses are more powerful than ever and capable of quantitative predictions, though care must still be taken in comparing results from theory and experiment. It is the main strength of the present Ph. D, which cover a multidisciplinary field combining physics, chemistry, theoretical and computational chemistry, and materials science pushing the boundaries for find and understand the structure and properties, at atomic level, of two types of materials: glasses (Ba2SiO4, high-BaSiO3, Ba4Si6O16, Ba5Si8O21, Ba6Si10O26, high-BaSi2O5 and low-BaSi2O5) and semiconductors (PbMoO4, In2O3, ZrO2, CaWO4 and SnMoO4/SnWO4). We discuss and present recent advances for understanding, by the use of first-principles quantum-mechanical calculations, at DFT level, their structural, electronic, and optical properties. We also studied the doping processes, the formation of solid solution, and phase transitions induced by pressure, that play key roles in the further development of these materials for optoelectronic and photocatalytic applications. We hope that present results guide the synthesis for the most promising candidates of a particular application.