Systematic first-principles electronic-structure study of carbon nanotubes

By using the local density approximation (LDA) in the framework of the density-functional theory, we study the electronic structure of all the chiral carbon nanotubes with the diameters between 0.8 nm and 2.0 nm. We find that the LDA result gives the reasonable energy gap and the density of states (DOS) by comparing with the STM/STS experimental result. We plot the peak-to-peak energy separations of the DOS as a function of the nanotube diameter. For the semiconducting nanotubes, we find the peak-to-peak separations can be classified into two types according to the chirality. This chirality dependence of the LDA result is opposite to that of the simple 9 tight-binding result.