Endofullerenes: size effects on structure and energy

The geometric and energy characteristics of endohedrals X@C-n (X = He, Ne, Ar; n = 20, 24, 30, 32, 40, 50, 60) were calculated by the density functional theory. The insertion of the helium atom leads to only a slight change in the geometry of the fullerene cage of the endohedrals. As the size of the trapped atom increases, the average C-C bond length increases in proportion to the radii of these atoms (by 0.05 Angstrom for Ne@C-20 and 0. 12 Angstrom for Ar@C-20). The inclusion energies of endofullerenes and the pressure of the cage exerted on the endo atom were calculated for all the above-mentioned endohedrals.