State of hydrogen molecules confined in C60 fullerene and carbon nanocapsule structures

The combination of PM3 semi-empirical method for geometry optimization, and ab initio DFT (density functional theory) for energy calculation, is used to study the configurations of hydrogen molecules at 0 K within the vacuum of C60 fullerene and carbon nanocapsules. The obtained structural information including the molecular arrangement and structural state of the clusters of H2 are mainly determined by two kinds of repulsive energies, namely that between the H2 molecules and the wall of the spheroidal or capsule like carbon structure, and that between interacting H2 molecules. It is further established that the repulsive energy among the H2 molecules is not purely a function of the number of encapsulated H2, and there is a tradeoff between the two kinds of repulsive energies.