Full text
| |
| Author(s): |
Liliana Yolanda Ancalla Dávila
Total Authors: 1
|
| Document type: | Doctoral Thesis |
| Press: | São Paulo. |
| Institution: | Universidade de São Paulo (USP). Instituto de Física (IF/SBI) |
| Defense date: | 2005-11-09 |
| Examining board members: |
Marilia Junqueira Caldas;
Lucy Vitoria Credidio Assali;
Rodrigo Barbosa Capaz;
Hélio Chacham;
Roberto Mendonça Faria
|
| Advisor: | Marilia Junqueira Caldas |
| Abstract | |
In this work we study the effect of packing, in different condensed forms, on the structural and electronic properties of a conjugated organic polymer, polyaniline, through theoretical simulations. The theoretical methodology that we used depends on the number of atoms of the chosen systems and also on the investigated properties. In this way, for films with thousands of atoms we used classical methods, in order to investigate structural properties. For the study of the electronic properties, we used quantum methods applied to crystalline systems. For the study of the structural properties of polyaniline films, it was necessary to parameterize a force field, and we chose the UNIVERSAL1.02 (UFF) field. The initial tests with the new field, UFFn, in crystalline films of polyaniline were successful, and we were able to obtain simulations of realistic homogeneous films for both reduced and oxidized systems. The density obtained for polymeric systems represents well the experimental value, and results of X-rays as a function of the radial distribution are very similar to those found in literature. By means of the ab initio SIESTA method, we studied the structural and electronic properties of molecular and lD and 3D crystalline systems of polyaniline, in the reduced and oxidized states. We verified the oxidation effect already for trimers of aniline. The inter-chain and intra-chain interactions of the crystalline systems are reflected in their electronic properties and were analyzed through the band structure and charge density. Different arrangements in the packing of the crystals reveal a significative effect in the transport properties of the material (AU) | |