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 for Ne@C₂₀ and 0.12 for Ar@C₂₀). The inclusion energies of endofullerenes and the pressure of the cage exerted on the endo atom were calculated for all the above-mentioned endohedrals.