Ab initio systematic study of chirality effects on phonon spectra, mechanical and thermal properties of narrow single walled carbon nanotubes

Pseudo-potential method under frame work of density functional perturbation theory (DFPT) has been utilized to calculate the phonon spectrum, phonon DOS, specific heat capacity and mechanical properties of narrow armchair and zigzag single walled carbon nanotubes (SWCNTs). Our calculations show that although their Young modulus are about 1 TPa, but armchair SWCNTs have greater compressive modulus than the zigzag tubes while the situation would be vice versa for tensile modulus. On the other hand, it was found out that specific heat capacity of narrow tubes shows chirality independence and decreases by increasing the radius of nanotube whereas, this is not the case for the wider ones. In addition, chirality dependence of the radial breadth mode (RBM) frequency of narrow SWCNTs has been shown.