Endohedral confinement of molecular hydrogen

Molecular hydrogen endohedrally confined using H2n-fullerene-like cavities is investigated with resort to density functional theory. Firstly, the pressure dependence of the ground state energy and internuclear distance of a single H2 molecule is obtained as a function of a H20 cage volume. Secondly, 30 hydrogen atoms are allowed to relax under the confinement of a H60 cage of radius R∼4 Å to reach a configuration of minimum energy. Hydrogen molecules form and self-assemble into a (H2)15 stable cluster characterized by two coaxial sixfold symmetry ring structures. The present confinement model gives results in agreement with experimental observations.