Rough hard sphere theory of the self-diffusion constant for molecular liquids

Abstract

A simple theory based on a hard sphere model is used to calculate the self−diffusion constant and the shear viscosity of liquid carbon tetrachloride. The theory accounts for the coupling between translational and rotational motions of molecules. This feature distinguishes the hard sphere theory presented herein with that given recently by other workers. It is shown that the coupling has a large (factor of 2) effect on the diffusion constant, and thus the coupling should not be neglected even for molecules as spherical as carbon tetrachloride. The approximations that are needed to arrive at a hard sphere theory for transport coefficients are discussed in detail. This analysis reveals the strengths and limitations of such a theory.