LATTICE-DYNAMICS OF THE ORIENTATIONALLY ORDERED CRYSTAL C-60

A calculation of the vibrational spectrum of intermolecular modes of t he low-temperature orientationally ordered crystalline phase of fuller ene C60 is carried out in the approximation of an intermolecular poten tial which includes two contributions: the atom-atom Lennard-Jones (12 -6) potential and a noncentral interaction. This model has allowed to approximate satisfactorily the experimental data on neutron scattering , temperature dependence of specific heat, and bulk modulus. Phonon di spersions, sound velocities, elastic constants, and densities of vibra tional states are calculated. It is shown that in the centre of the Br illouin zone librational modes which are Raman active should be locate d in the region 20 to 30 cm-1 and infrared active translational modes should be in the range 40 to 60 cm-1.