FIRST-PRINCIPLES CALCULATIONS OF THE RADIAL BREATHING MODE OF SINGLE-WALL CARBON NANOTUBES

The radial breathing mode is a promising candidate for the analysis of conformational and electronic properties of carbon nanotubes. The pap er presents calculations based on the local density approximation to d etermine the radial breathing mode (RBM) frequency of various zigzag a nd armchair tubes with radii between 3.5 and 8.1 Angstrom. The frequen cies are derived from both frozen phonon calculations for nanotubes an d from the elastic constants of the flat graphene sheet. The RBM frequ ency of the (10,10) armchair tube is found to be 175 cm(-1) and 174 cm (-1) for the two techniques, respectively. These values are in very go od agreement with one of the strongest components in the structured Ra man band of the radial breathing modes observed at 177 cm(-1). Since t he RBM frequency turns out to scale with 1/R the calculations also all ow one to evaluate the frequency of this mode for tubes with arbitrary chirality. [S0163-1829(98)51638-4].