Nonconformal potentials and second virial coefficients in molecular fluids. II. Applications to nonspherical molecules

A theory recently proposed characterizes effective two-body interactions in gases by molecular sizes and energies plus effective measures of the nonco nformality between the exact potential and a spherical reference. This theo ry provides a procedure to construct effective potentials which reproduce t he second virial coefficients B(T) of the substance of interest and allows us to express B(T) in simple and compact form. In this paper we test the ap plicability of the theory to a variety of nonspherical models-spherocylinde rs, ellipsoids, Lennard-Jones polyatomics, square-well chains, and Stockmay er molecules-and show that their virial coefficients are accounted for accu rately by the theory. The theory is used to study the effects of molecular geometry, particularly the elongation of linear molecules, on the angle ave raged molecular parameters and on the effective potential. The effective po tentials of the models considered are obtained, and the effects of size and geometrical shape are discussed.