Thermodynamic properties of simple multi-Yukawa fluids: a variational approach

Abstract

The perturbation theory of dense fluids interacting according to an intermolecular potential represented as a linear combinations of m-Yukawa functions, whose reference interaction is the hard-sphere potential, allows setting an equation of state in terms of the ratio $\lambda $ of the corresponding species molecular sizes. In this work we determine $\lambda $ by solving numerically the non-linear equation that results from the minimization of the system Helmholtz free energy. The resulting values of $\lambda $ are density and temperature dependent, and are in quantitative agreement with those from the development of Mansoori and Canfield. The proposed method also provides the compressibility factor of the corresponding Lennard-Jones fluid, represented by the combination of a hard-sphere plus two Yukawa terms, in good agreement with the available values from Monte Carlo simulations.