A REALISTIC MOLECULAR-DYNAMICS SIMULATION OF THE PLASTIC CRYSTALLINE PHASE OF NEOPENTANE .2. INDIVIDUAL ORIENTATIONAL DYNAMICS

For a ''realistic'' model of the ODIC phase of neopentane, the single, particle orientational dynamics is analyzed; the data has been obtained previously by a molecular dynamics simulation. The orientational motion of the molecules from one potential well to another is studied by analyzing their orientational trajectories directly and through the temporal self correlation of an appropriate symmetrized rotator function. Self correlation functions of other rotators give information on the librational motion of the molecules at the bottom of the orientational potential wells. The mean orientational potential is shown to better represent this librational motion than the reorientational dynamics. The method for determining which rotator functions have to be used to describe the different types of motion makes use of the symmetry group of the orientational wells.