Theoretical calculation for the ultraviolet optical properties of single-walled carbon nanotubes

We present a theoretical study of the ultraviolet (UV) optical properties of carbon nanotubes based on the local-density approximation in density functional theory and the generalized tight-binding approximation. Our calculations indicate that the absorption spectrum in the UV region depends strongly not only on nanotube diameter but also on chiral index. In zigzag nanotubes with even indices, peculiar features in the UV absorption spectrum emerge. In sharp contrast, these features are absent from the spectrum of zigzag nanotubes with odd indices. These spectral features are characteristic of interband transitions near the M point of the hexagonal Brillouin zone of graphene