Global crossover equation of state of a van der Waals fluid

A global crossover equation of state that incorporates the classical van de r Waals behavior (including the ideal-gas limit and the high-density hard-s phere limit) far away from the critical point and the singular behavior nea r the critical point has been developed. It is based on a transformation de rived from the renormalization-group theory of critical fluctuations to the classical van der Waals equation of state. The crossover van der Waals equ ation contains only one non-universal system-dependent parameter associated with the range of intermolecular forces and it shows how the density fluct uations affect all thermodynamic properties more and more significantly whe n the fluid approaches the critical point. In particular, the critical comp ressibility factor which for the classical van der Waals equation is Z(c) = 0.375, becomes suppressed to a more realistic value of 0.26-0.29 as is typ ical for simple fluids. (C) 1999 Elsevier Science B.V. All rights reserved.