Third Virial Coefficients. Three-Body Dispersion Interactions between Asymmetric Molecules

Abstract

This work examines corrections to the third virial coefficient arising from three-body dispersion forces of the Muto–Axilrod–Teller type between asymmetric molecules. The corrections are derived for mixtures of gases composed of molecules of arbitrary asymmetry and are examined through the second order of a perturbation treatment. A Lennard-Jones (12–6) or (18–6) potential is assumed to describe the spherically symmetric component of the two-body potential for overlap and dispersion interactions. The first-order correction for asymmetric molecules is found to be identical in form to that previously found for spherical molecules. Examples of the second-order corrections are given for CO2, where they are large enough to require consideration in a comparison between theory and experiment, and for a more nearly spherical molecule, N2, where they are relatively small.