Phonon and thermal properties of achiral single wall carbon nanotubes

Barkatullah University Department of Electronics 462 026 Bhopal India
Pramana (Impact Factor: 0.56). 08/2006; 67(2):305-317. DOI:10.1007/s12043-006-0075-0

ABSTRACT A detailed theoretical study of the phonon and thermal properties of achiral single wall carbon nanotubes has been carried
out using force constant model considering up to third nearest-neighbor interactions. We have calculated the phonon dispersions,
density of states, radial breathing modes (RBM) and the specific heats for various zigzag and armchair nanotubes, with radii
ranging from 2.8 Å to 11.0 Å. A comparative study of phonon spectrum with measured Raman data reveals that the number of Raman
active modes for a tube does not depend on the number of atoms present in the unit cell but on its chirality. Calculated phonon
modes at the zone center more or less accurately predicted the Raman active modes. The radial breathing mode is of particular
interest as for a specific radius of a nanotube it is found to be independent of its chirality. We have also calculated the
variation of RBM and G-band modes for tubes of different radii. RBM shows an inverse dependence on the radius of the tube.
Finally, the values of specific heat are calculated for various nanotubes at room temperature and it was found that the specific
heat shows an exponential dependence on the diameter of the tube.

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