Método pseudomolecular para a obtenção das constantes elásticas utilizando um potencial de modelo de rede

• Ano de defesa: 2014
• Autor(a) principal: Simonário, Patrick dos Santos
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Estadual de Maringá; Brasil; Departamento de Física; Programa de Pós-Graduação em Física; UEM; Maringá, PR; Centro de Ciências Exatas
• Palavras-chave em Português: Método pseudomolecular; Constantes elásticas; Modelos de rede; Brasil.; Pseudo-molecular method; Elastic constants; Lattice models; Brazil.; Ciências Exatas e da Terra; Física
• Link de acesso: http://repositorio.uem.br:8080/jspui/handle/1/2713

The main subject of this work is describe the nematic liquid crystals from a theoretical point of view, by means of the elastic theory. In this theory, among several other methods, the pseudo-molecular method is used to determine the elastic constants of the sample. It will be shown some models which may be found in the literature and also the model used as a base of this work. The contribution here was to describe the elastic constants of a nematic liquid crystal using the pseudo-molecular method for a intermolecular interaction pair potential. The potential used in this work is a variation of a lattice model (proposed by Huphries, Luckhurst and Romano in 1981), in which was obtained physical parameters using computational methods and Monte Carlo simulations. It was obtained new results for the elastic constants, adapting the lattice model to the pseudo-molecular model. The work is divides as it follows. Firstly, it will be discussed some important historical facts about the liquid crystal; then, its fases and classifications, which brings one to the nematic liquid crystals, the main character of this work, being careful to show the problem and some relevant physical quantities, like the director vector, the tensorial parameter of order, the elastic density of energy and, consequently, the elastic constants, which will be defined with more attention. After that initial part, the pseudo-molecular method is defined, taking into account the shape of the interaction volume which, in this case, has an ellipsoidal shape, with the eccentricity being the parameter that defines it. The pseudo-molecular method is built for an generic potential of interaction, which has all the cases studied in this work as particular ones. These cases will be used to illustrate how to use the method to determine the elastic constantes in a sample of nematic liquid crystal. Lastly, the method will be used in the lattice model potential and the elastic constants will be found, analitically, as functions of the anisotropy of the polarizability and the eccentricity.