A molecular dynamics study of dielectric friction

Abstract

A molecular dynamics study of the friction experienced by the dye molecule resorufamine rotating in a polar solvent is performed. The validity of simple continuum theories of dielectric friction is tested. It is found that the Alavi–Waldeck theory gives reasonable results for the zero frequency dielectric friction coefficient while the Nee–Zwanzig theory requires an unphysically small cavity radius. A procedure for evaluating the time dependent friction kernel from torques and angular velocities, which enables the contributions to the friction from the van der Waals and Coulomb forces to be evaluated separately, is suggested. This study of a realistic system shows that electrostatic interactions can enhance friction by at least two physical mechanisms. First is a contribution to the friction which arises solely from retardation of the solvent reaction field. Second is a contribution arising from local structural changes of the solvent which are driven by the electrostatic field, i.e., a change in the local viscosity.