Various polygonal defects which retained the 3-bonded characteristics of C were proposed as disclinations. The n-gonal defects, where n was an integer that was less than 5, were responsible for forming cones and were less stable than the pentagonal defects, in an hexagonal network, which were responsible for the formation of spherical fullerenes such as C60. On the other hand, the n-gonal defects (where n was greater than 6) corresponded to negative wedge disclinations on the surface and led to a negatively curved surface. By using molecular dynamics simulations, it was found that surfaces which contained decagonal, hendecagonal or dodecagonal defects were more stable than were similarly shaped surfaces which contained a multiple number of heptagons. It was also found that surfaces which contained an n-gonal defect (where n had a large value), with a periodic folding of the surface, were stable in some cases. In particular, a buckled surface with an octadecagonal defect which was rolled (with surface distortions bending upwards and downwards 3 times around the defect) gave a stable structure. The present analysis indicated that complex structures which had not previously been considered might exist.
S.Ihara, S.Itoh, K.Akagi, R.Tamura, M.Tsukada: Physical Review B, 1996, 54, 14713-9