Virial Coefficients for Square-Well Potentials

Abstract

A comparatively simple method for evaluating virial coefficients for square‐well potentials is investigated. The method is based on the fact that a square‐well function can be expressed as a sum of step functions. Calculations are made for the third virial coefficient and for the fourth virial coefficient. The results for the third virial coefficient are in agreement with published values but the calculated fourth virial coefficients differ from those in the literature. Our values are confirmed by comparison with values derived by an entirely different method which we describe elsewhere. Critical constants are calculated on the assumption that fifth and higher virial coefficients may be neglected at the critical density.