Low-temperature heat capacity of fullerite C60 doped with nitrogen

The heat capacity Cm of polycrystalline fullerite C60 doped with nitrogen is measured in the temperature interval 2–13K. The contributions to the heat capacity from translational lattice vibrations (Debye contribution), from orientational vibrations of the C60 molecules (Einstein contribution), and from the motion of the N2 molecules in the octahedral cavities of the C60 lattice are estimated. However, no indications of the first-order phase transformation detected earlier in a dilatometric investigation of the N2–C60 orientational glass are found (beyond the experimental error limits). A possible explanation for this fact is proposed.