Benedek, G., E. Galvani, et al. (1995). "A hypothetical new class of superhard materials." Il Nuovo Cimento D 17(1): 97-102.

By means of topological arguments we predict a new class of 4-coordinated covalent carbon lattices having a hollow structure (hollow diamonds (HDs)). A calculation of their structural and elastic properties based on the Tersoff potential indicates a stability and hardness very close to, albeit smaller than diamond. However, the intercalation of the smallest HDs with either mono- or divalent ions is estimated to give new nanocomposite materials which are harder than diamond.