General features of the energetics and electronic states of carbon nanotubes, containing pentagon-heptagon pair (5/7) topological defects in the hexagonal network of the zig-zag configuration, were investigated using simple tight-binding models. This 5/7 pair defect on the nanotube structure was not only responsible for a change in nanotube diameter, but also governed the electronic behavior around the Fermi level. Furthermore, nanotubes having different helicities and different electronic properties could be connected using such a pair. Various configurations including one, two and three 5/7 pairs were explored in order to understand the influence of several defects upon the electronic properties of the system. Topological aspects associated with the presence of 5/7 pair defects in armchair and chiral nanotubes were also considered.

Structural and Electronic Properties of Pentagon-Heptagon Pair Defects in Carbon Nanotubes. J.C.Charlier, T.W.Ebbesen, P.Lambin: Physical Review B, 1996, 53[16], 11108-13