Orthogonal polynomial approach to fluids with internal degrees of freedom: The case of nonpolar, polarizable molecules

Abstract

The molecules of real liquids have internal degrees of freedom that may couple with the external ones of position and orientation so that they affect and are affected by the microscopic liquid structure. For cases where the internal coordinates possess a Boltzmann-like distribution, a procedure is described whereby such coordinates can be incorporated into the conventional formulation of classical liquid theory with no approximations beyond some reliable closure relation familiar from simple liquids. The basis of the procedure is expansions in appropriate orthogonal polynomials of the internal coordinates. This program is successfully carried out for a classical model of nonpolar, polarizable molecules treated as Drude oscillators, generalizing published solutions of the mean spherical approximation for the same model.