INVESTIGATIONS OF DIAMOND-GRAPHITE HYBRIDS AND FULLERENES WITH 7-MEMBERED RINGS

The nature of diamond-graphite hybrids has been studied by molecular m echanics, by examining the structures of species such as C84Hx wherein the sp(3) to sp(2) carbon ratio is varied progressively. The dependen ce 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 C110Hx and in a diamond-like C120Hx as a function of the sp(3)/sp(2) carbon atom rat io. The gap increases exponentially with the fraction of sp(3) carbon. Shapes of fullerene-like structures with 7-membered rings, in additio n to 6- and 5-membered rings, have been investigated along with struct ures of bent nanotubes having similar ring systems. (C) 1997 Elsevier Science B.V.