Using the extended Su-Schriffer-Heeger model in real space, an investigation was made of the electronic properties of carbon nanotubes, containing pentagon-heptagon pairs (5/7), pentagon-hexagon-heptagon (5/6/7) and pentagon-hexagon-hexagon-heptagon (5/6/6/7) topological defects in the perfect hexagonal network of the zig-zag configuration. The calculations showed that the pentagon-heptagon pair defects in the nanotube structure were responsible not only for a change in nanotube diameter, but also governed the electronic behavior around the Fermi level. By calculating the densities of states of the (9,0)-(8,0), (9,0)-(7,0) and (9,0)-(6,0) systems, the densities and bands of these heterojunctions were compared. The results showed that the various arrangements of pentagons and heptagons along the axis had obviously different effects upon the electrical properties of carbon nanotubes.

Electronic Properties of Single Carbon Nanotubes with Pentagon-Heptagon Pairs Defects. H.F.Hu, L.F.Zhang, X.Z.Wang, J.W.Liang: Journal of Computational Physics, 2004, 21[3], 369-72