A thermodynamic and kinetic study of the formation of C20 compounds encapsulating H, He and Ne atoms

Binding energies of helium, neon and atomic hydrogen encapsulated inside a C-20 cage were calculated using an ab initio method at the B3LYP/6-31+Gstar level of theory. The standard equilibrium constants for the reactions of noble-gas atoms going into the C-20 molecular cage have also been studied. The transition states for the reactions of C-20 with hydrogen and helium were further obtained with an ab initio method at the B3LYP/6-31+Gstar level and the rate constants were estimated by using conventional transition-state theory. It was found that the hydrogen and helium atoms are extremely difficult to put into the C-20 cage. Once inside the cage, a helium atom can hardly get out, while a hydrogen atom can easily escape from the cage. The results are expected to enrich fullerene science and be helpful for fullerene applications such as storage.