Dipole polarizabilities of noble gas endohedral fullerenes

First-principles calculations were performed on the polarizabilities of noble gas endohedral complexes, X@C60 (X = He–Kr). The polarizability of X@C60 increases from He–Kr, but is distinctly smaller than the sum of the X atoms and C60, unlike many other non-bonded systems for which an additive rule holds. Compared to C60, the increased polarizabilities in X@C60 are mainly from the enhanced charge transfer contribution of the cage and the local polarization of the interior X atoms, though the interior atoms are found less polarized than the corresponding free ones.