Polarized Raman spectra of oriented monoclinic single crystals of α-Bi 2 O 3 have been obtained at temperatures of 20-650 K in the region 15-3500 cm −1 . The assignment of the Raman bands to the A g and B g modes was given. The photoinduced reduction of the Raman intensity was observed after heating a crystal above 500 K, and cooling it down to room temperature, under laser irradiation. A lattice dynamical analysis based on two-particle interatomic potentials and a rigid-ion model was performed. These potentials were consistent with the Raman and IR data, besides which they showed a stable dynamics throughout the Brillouin zone, and yielded the minimum of internal forces and pressures in the crystal lattice. The phonon dispersion curves, and the projected and total densities of phonon states were calculated.

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A calculation of the vibrational spectrum of intermolecular modes of the low-temperature orientationally ordered crystalline phase of fullerene C,, is carried out in the approximation of an intermolecular potential 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 dispersions, sound velocities, elastic constants, and densities of vibrational states are calculated. It is shown that in the centre of the Brillouin zone librational modes which are Raman active should be located in the region 20 to 30cm-' and infrared active translational modes should be in the range 40 to 60 cm-I.

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