Reorientational correlation functions for computer-simulated liquids of tetrahedral molecules

Molecular dynamics simulations have been carried out on fluids of tetrahedral molecules for several sets of temperatures and pressures. The results were analysed to give reorientational and angular velocity autocorrelation functions. It was found that these could be related by a cumulant expansion in powers of the angular velocity and rotation operators. This type of analysis is likely to prove simple and useful for relating orientational correlation functions to the angular velocity correlation function in dense fluids where reorientation is hindered.