We present first principles calculations on the band structures of 20 different small diameter (d) single wall carbon nanotubes (SWCNTs), considering those tubes which are metallic in simple zone folding picture, including 6 chiral ones, employing density functional theory (DFT). The band gaps are calculated and discussed for all of the tubes. The Fermi wave-vector of armchair tubes shows a downshift from its ideal, zone folding expected value; this shift is proportional to 1/d2. Four zigzag and four chiral tubes show a small gap in the band structure. A higher order correction term appears in the diameter dependence of the gap for the zigzag tubes, the magnitude of which is apparently overestimated. This overestimation can likely be eliminated by considering many-electron effects.
展开▼
