Force and torque correlations in diatomic fluids

Abstract

A simple relationship is derived between the mean squared force and mean squared torque in homonuclear diatomic fluids which successfully accounts for published simulation data spanning a wide range of bond lengths and densities in the liquid range for molecules without quadrupole moments. Modifications required in heteronuclear systems are discussed and found to be consistent with the scant information available in this area. The expression for homonuclear systems can be extended to explain the relation between the force and torque time correlation functions in these and triatomic fluids. Finally, the results are used to link the parameter κ, introduced by Kivelson et al., to the slip limit friction coefficient for molecular reorientation.