Elementary Description of the Equation of State of a Simple Fluid

Abstract

In this paper we describe an improved equation of state for classical fluids. We consider a system of molecules interacting with a Lennard‐Jones potential with a rigid‐sphere cutoff. An algorithm for the equation of state is based on the idea that the major contributions to the pressure arise from the statistical geometry imposed by the rigid‐core repulsion, the mean field acting on a molecule, and a limited number of fluctuations about the mean field. The rigid‐core contribution is calculated from the solution to the Percus‐Yevick equation, and the mean field directly from the corresponding theoretical radical distribution function. The first five fluctuation terms are computed. The equation of state of argon is calculated at a temperature slightly above its critical point, and at a high temperature (T* = 2.74) . The results are found to be in good agreement with experiment.