Rattling of ellipsoidal particles in a three-dimensional system

Molecular dynamics simulations of 256 ellipsoidal particles are carried out for constant temperature and densities corresponding to an isotropic phase of the system. We consider components of the velocity perpendicular to the molecular axis, and the velocity and velocity-sign autocorrelation functions are analysed using a model based on uncorrelated successive velocity reversals. In calculations of the time intervals between successive velocity reversals we use two criteria: ‘Cartesian coordinate oscillations’ and ‘right-angle turns’. Our results show that the two criteria are not equivalent and the model gives a proper description of the velocity-sign correlation functions for the ‘coordinate oscillation’ criterion only.