Universal density of states for carbon nanotubes

=The density of states in the vicinity of the Fermi level of single-wall carbon nanotubes can be expressed in terms of a universal relationship that depends only on whether the nanotube is metallic or semiconducting. We compare the predictions of this approximate relationship with densities of states calculated using first-principles band structure results. These comparisons show that: this approximation works well for energies within about 1 eV of the Fermi level. [S0031-9007(98)07 132-4].