Molecular dynamics simulation of solid C-60 under progressively raised pressure

Recent molecular dynamics investigations have shown that C-60 fullerites ca n be investigated by means of simple potentials and few calculations have f ocused on the pressure dependence of thermodynamic properties and the induc ed order-disorder phase transition. The aim of this work is to perform mole cular dynamics simulation of the C-60 crystal lattice in the face centred c ubic structure under progressively raised pressure, to illustrate the limit s of the crude pseudo atom approach and the validity of the potential in th e rigid molecule, when seeking for possible phase transitions. For that pur pose, several thermodynamic and structural proper ties are calculated with different potential models in the pseudo atom approach and as a rigid freel y rotating C-60 molecule. Calculated properties are compared to experimenta l data. It will be demonstrated that though the pseudo atom approach is rea sonable in the low-pressure region (< 4 kbar), the rigid molecule is in bet ter agreement with experiments depending on the choice of the model potenti al and the pressure applied. Orientational transition pressures are observe d at 5 and 260 K, the distorted lattice and the cell contraction are measur ed and the density of phonon states is reported at different pressures.