C60O - A MOLECULAR-DYNAMICS STUDY OF ROTATION IN THE SOLID-PHASE SOLID-PHASE

Constant-pressure molecular dynamics simulations have been performed for solid C60O using a pair-wise additive atom-atom potential. The simulation results suggest that the presence of oxygen atoms on C60 framework does not change the lattice structure significantly. The onset of the orientational freezing is predicted to occur in a similar temperature range as pure C60. The molecular dipoles prefer to point along crystal (100) directions so that the oxygen atom can occupy one of the vacant octahedral sites. Since the cavity associated with the octahedral site is large, solid C60O has the same structure as C60 (i.e. f.c.c.) with essentially the same room-temperature lattice parameter. At room temperature, the C60O molecules are found to be rotating anisotropically. This prediction could be tested by appropriate NMR measurements.