The general features of the energetics of nano-tubes which contained pentagon-heptagon 5/7 topological pair defects in the hexagonal network of the zig-zag configuration were investigated by using simple tight-binding models. The 5/7 pair defect in the nano-tube structure was responsible not only for a change in nano-tube diameter, but also governed the electronic behavior around the Fermi level. It was noted that nano-tubes which had differing helicities and differing electronic properties could be linked by means of such a pair. Various configurations, including one, two, and three 5/7 pairs were examined in order to determine the effect of several defects upon the electronic properties of the system. Topological aspects were associated with the presence of 5/7 pair defects in armchair and chiral nano-tubes.

J.C.Charlier, T.W.Ebbesen, P.Lambin: Physical Review B, 1996, 53[16], 11108-13