The radial breathing mode of carbon nanotubes

We report an extensive set of results for the radial breathing modes (RBM) of infinite and finite length single walled carbon nanotubes using the second generation reactive empirical bond order potential (REBO) developed by Brenner et al. As expected, the frequency, nu of the RBM is inversely proportional to the nanotube radius, R-0 , nu=alpha/ R-0. We find two different linear fits to the data, one for zigzag tubes (3.25 THz nm) and one for armchair tubes (alpha=3.18 THz nm). For finite tubes, the RBM rapidly approaches the infinite length value for nanotubes greater than 5 nm in length.