Vidros: sólidos ou líquidos? Uma análise via simulação computacional

• Ano de defesa: 2019
• Autor(a) principal: Michelin, José Vitor
• Orientador(a): Rino, José Pedro
• Tipo de documento: Tese
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal de São Carlos; Câmpus São Carlos
• Programa de Pós-Graduação: Programa de Pós-Graduação em Física - PPGF
• Palavras-chave em Português: Vidro; Relaxação; Cinética; Dinâmica molecular; Transição Vítrea
• Palavras-chave em Inglês: Glass; Relaxation; Glass Transition; Kinetics; Molecular dynamics
• Área do conhecimento CNPq: CIENCIAS EXATAS E DA TERRA::FISICA::FISICA GERAL::FISICA ESTATISTICA E TERMODINAMICA; CIENCIAS EXATAS E DA TERRA::FISICA::FISICA DA MATERIA CONDENSADA; CIENCIAS EXATAS E DA TERRA::FISICA::FISICA GERAL
• Link de acesso: https://repositorio.ufscar.br/handle/ufscar/12016

For many centuries there were different definitions of what glass would be, this discussion persists to current days. Is glass a solid or liquid material? In this work, we answer this question through computational simulations of the main properties of the crystalline solid, liquid and glass materials, comparing its behavior and results. We studied four types of materials models, silicon (Si), zirconium (Zr), silica (SiO 2 ) and alloy of Zr 50 Cu 50 . We have shown that there is a physical change in the process of between the supercooled liquid and the glass, which relates the high viscosity that the glass has with the relaxation time. Based on our results, we affirm that glass does not is a solid nor a liquid, it is a state of matter unique and we create a new definition for it: Glass, within a human time scale, is a physical states of matter with a globally amorphous structure, containing nuclei organized at medium atomic distances throughout the material. It has a temperature called the glass transition, where ergodicity is broken kinetically. Below this temperature, the relaxation time and viscosity increase infinitely, giving the material mechanical rigidity. This state of matter is not thermodynamically stable, which causes it to relax spontaneously over time, with the crystal as its final destination over a very large time limit.