Heat capacity of endohedral fullerenes Rg@C60 (Rg = He, Ne, Ar and Kr)

The heat capacity of rare gas containing endohedral fullerenes has been computed by computing the vibrational frequencies of the molecules using the Hartree-Fock method and the density functional theoretic method with the wB97XD functional and the 6-31G* basis set. The consequences of the translational motion of the rare gas atom becoming vibrational motion inside the fullerene cavity are examined by comparing the computed vibrational frequencies for fullerene and the endohedral fullerenes. The increase in the heat capacity of the endohedral fullerenes due to encapsulation is interpreted in terms of the bound states of a three dimensional isotropic harmonic oscillator.