Investigations of diamond-graphite hybrids and fullerenes with seven-membered rings

The nature of diamond-graphite hybrids has been studied by molecular mechanics, by examining the structures of species such as C84H x wherein the sp3 to sp2 carbon ratio is varied progressively. The dependence of the average coordination number on the atom fraction of hydrogen has been examined in the light of the random covalent network model. The HOMO-LUMO gap has been estimated in a graphite-like C110H x and in a diamond-like C120H x as a function of the sp 3 sp 2 carbon atom ratio. The gap increases exponentially with the fraction of sp3 carbon. Shapes of fullerene-like structures with 7-membered rings, in addition to 6- and 5-membered rings, have been investigated along with structures of bent nanotubes having similar ring systems.