STABILITY OF M-AT-C-60 ENDOHEDRAL COMPLEXES

M @ C60 endohedral complexes, which are based on the C60 molecule and contain encapsulated atoms M, would provide a unique opportunity to tailor specific properties of the C60 system on a molecular level. The stability of these complexes is calculated using a Born-Haber cycle that was originally applied to determine the formation enthalpy of solid C60 intercalation compounds. We find that the formation energy of M @ C60 depends crucially on the ionization potential and electron affinity of the endohedral atom and the C60 molecule. A significant contribution to the formation energy comes from the polarization energy of the cage if the enclosed atom is not at the cage center; this finding is in agreement with available ab initio results. We discuss the potential of these systems to become a new class of superconducting materials.