Tesis
Estudo por dinâmica molecular da transição de fase estrutural de nanotubos de carbono por indução de pressão: um método ab initio
Fecha
2012-10-26Registro en:
VENDRUSCULO, Bruno de Oliveira. Ab initio molecular dynamics study on pressure-induced structural phase transition of carbon nanotubes. 2012. 65 f. Dissertação (Mestrado em Física) - Universidade Federal de Santa Maria, Santa Maria, 2012.
Autor
Vendrusculo, Bruno de Oliveira
Institución
Resumen
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.