Comparison of Two Theories for the Two Particle Distribution Function of Polar Fluids

Abstract

Two recent theories for the two particle distribution function of polar fluids are compared. The formal theory of Nienhuis and Deutch [J. Chem. Phys. 55, 4213 (1971)] is valid for arbitrary sample geometry and arbitrary short‐range forces accompanying the dipole‐dipole interactions. The theory of M. S. Wertheim [J. Chem. Phys. 55, 4291 (1971)] presents an exact result for the mean spherical model (MSM) of a fluid of hard spheres with embedded dipole moment in an infinite system and in a finite spherical system. Perfect agreement is found when the approximations of the MSM are introduced into the Nienhuis‐Deutch theory. This lends strong support to the conclusions that have been drawn about the long‐range and shape dependent nature of the two particle distribution function for polar systems. Finally an expression is given for the excess free energy of a dipolar fluid in the MSM.