Solution of a new integral equation for pair correlation functions in molecular liquids

Abstract

This paper discusses the first numerical solutions of the reference interaction site model (RISM) equation which was proposed by Chandler and Andersen [J. Chem. Phys. 57, 1930 (1972)] to provide a theory for the equilibrium pair correlations of molecular fluids in which the ``molecules'' are composed of fused hard spheres. The particular system studied herein is a one component fluid in which the molecules are symmetric ``diatomics'' (i.e., each is formed by two hard spheres of diameter σ with the centers of the spheres a distance L from each other). It is shown that the accuracy of the RISM equation for this molecular fluid is comparable to that of the Percus‐Yevick equation for dense hard sphere fluids. Numerous calculations are presented which illustrate the usefulness of this theory in providing a detailed description of the intermolecular structure of complex fluids. One calculation provides a theory for the structure of liquid nitrogen.