ab initio study of chirality effects onphonon spectra, mechanical and thermal properties of nearly samediameter single wall carbon nanotubes

in this paper, we have used density functional perturbation theory (dfpt) and pseudo-potential method to calculate the phonon spectrum, phonon density of states (dos), specific heat capacity and mechanical properties of (5,5) armchair and (9,0) zigzag single wall carbon nanotubes (swcnts). our calculations show that young’s modulusfor (5,5) and (9,0) nanotubesare higher than 1tpa. we have also shown that the value of compressive young’s modulus for (5,5) nanotube isgreater thanthat for (9,0) nanotube while thevalue of tensile young’s modulus for (9,0) nanotubeisgreater than that for(5,5) nanotube. the result of our calculations shows that thespecific heat capacity of (5,5) and (9,0) nanotubes coincides, therefore we may conclude that thespecific heat capacity of nanotubes is independent of their chirality. furthermore we have found that the atoms in the armchair nanotubes are positioned as close as possible in the direction of the nanotube axis, therefore they could have more resistant against compressive pressure