Global thermodynamic behavior of fluids in the critical region

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Abstract
In a preceding publication [Z. Y. Chen, P. C. Albright, and J. V. Sengers, Phys. Rev. A 41, 3161 (1990)] a procedure for constructing a thermodynamic free energy of fluids was proposed that incorporates crossover from singular behavior at the critical point to regular behavior far away from the critical point. In the present paper this procedure, based on an approximate solution of the renormalization-group theory of critical phenomena, is further extended so that it can be used in conjunction with a six-term classical Landau expansion. The resulting thermodynamic free energy yields a satisfactory representation of the thermodynamic properties of fluids in a large range of temperatures and densities around the critical point, as is demonstrated by a comparison with experimental thermodynamic-property data for carbon dioxide, steam, and ethane.