Análise da potencialidade a condução do BDT através da densidade eletrônica de estados via tight binding e desenvolvimento de software (B3J)
In this work we studied the potentiality of the polymer BDT (1,3-benzodithiole 4Hciclopenta[2,1-b:3,4b’]) to become a conducting polymer. Ground state conformations and the electronic structure have been calculated through quantum chemical methods in order to obtain the density of electronic states....
| Autor principal: | GUIMARÃES, Jeconias Rocha |
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| Grau: | Dissertação |
| Idioma: | por |
| Publicado em: |
Universidade Federal do Pará
2014
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| Assuntos: | |
| Acesso em linha: |
http://repositorio.ufpa.br/jspui/handle/2011/5056 |
| Resumo: |
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In this work we studied the potentiality of the polymer BDT (1,3-benzodithiole 4Hciclopenta[2,1-b:3,4b’]) to become a conducting polymer. Ground state conformations and the electronic structure have been calculated through quantum chemical methods in order to obtain the density of electronic states. The presence of several types of conformational defects and the variation of doping level has been considered. One of the most used theories to study the doping effects on conjugated polymers is the Huckel method. It is based on the separability of the sigma and pi bonds of planar molecules. BDT oligomers are not planar molecules and an extended Huckel method that includes all the atomic valence functions
has been used. An original computation code, the B3J program, has been developed for this purpose. Simulations of the absorption spectrum in the UV-visible-near IR region have seen performed as well. Program B3J calculates the density of states of polymeric systems. The band structure of BDT was obtained with this software. We calculated the density of states of the neutral system and doped systems including several doping levels and both random and
uniform distribution of defects. The square of the coefficients expansion of the wave
function was obtained for polymers including up to 20 monomers. For these calculations
we used geometries calculated by AM1 and PM3 quantum chemical methods. Finally, we studied the asymmetry of the charge separation induced by the presence of an external static electrical field in BDT oligomers suitably substituted by electron
acceptor/donor species. The results are consistent with a transistor-like behavior of neutral
and charged molecules. |