Estudo por dinâmica molecular da transição de fase estrutural de nanotubos de carbono por indução de pressão: um método ab initio

• Ano de defesa: 2012
• Autor(a) principal: Vendrusculo, Bruno de Oliveira
• Orientador(a): Silva, Leandro Barros da
• Banca de defesa: Dorneles, Lucio Strazzabosco , Rossato, Jussane
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: por
• Instituição de defesa: Universidade Federal de Santa Maria
• Programa de Pós-Graduação: Programa de Pós-Graduação em Física
• Departamento: Física
• País: BR
• Palavras-chave em Português: Nanotubos; Pressão hidrostática; Transição estrutural; Simulação computacional
• Palavras-chave em Inglês: Nanotubes; Hidrostatic pressure; Estructural transition; Computation simulation
• Área do conhecimento CNPq: CNPQ::CIENCIAS EXATAS E DA TERRA::FISICA
• Link de acesso: http://repositorio.ufsm.br/handle/1/9232

This work aims to study the computational training of new phases of materials based on carbon nanotubes using as precursor materials. The procedure consists in simulate bundle formed by carbon nanotubes (NTC) (5, 5), (6, 6) and (7, 7) under hydrostatic pressure of 10, 15, 20, 25 and 30 GPa The present study was through the method of ab initio molecular dynamics, as implemented in the SIESTA code. The bundles of nanotubes were studied through a unit cell containing four nanotubes, using the periodic boundary conditions. As a result, for nanotubes (5, 5) of 10 GPa it has occurred a phase transition similar to graphite, which has graphene sheets stacked with the atoms distant from the first neighboring 1.42 Å, indicating the formation of a structure rich in sp2 hybridization. By applying to the nanotubes 30 GPa (5, 5) and (7, 7), there was an amorphous structure similar to cubic diamond with carbon atoms distant from the first neighboring 1.54 Å, indicating a phase with rich sp3 bonds. Finally, for all other combinations, the results were the transition to amorphous structures, varying according to the diameter of the nanotube and the pressure applied, the ratios of sp2 and sp3 carbon, as well as the distances found for the first neighbors were approximately 1.48 Å indicating the formation of transitional phases between sp2 and sp3 hybridizations.