Abstract
The diamond-interior C100 molecule has been studied with a local-density-functional cluster method and found to be unstable with respect to a Jahn-Teller distortion. More seriously, the original diamondlike structure is unstable; the molecule spontaneously decomposes into an inner C20 core trapped iside an outer C80 fullerenelike shell. In essence, tetrahedral bonding throughout the molecule gives rise to 60 dangling bonds at the surface, which give way to 20 dangling bonds on the inner C20 surface in the double-shell fullerene. As expected, hydrogen stabilizes the tetrahedral bonding in C100H60.