Improved analytical thermodynamic properties of the triangular-well fluid from perturbation theory

Abstract

In this short communication, it is shown that the triangular-well fluid analytic equation of state (EOS) recently proposed by Betancourt-Cárdenas et al. [Mol. Phys. 105 (2007) 2987] within the framework of the Barker–Henderson perturbation theory of fluids with the macroscopic compressibility approximation (BH-MCA) can be improved in two ways. First it is cast into a more compact form, which avoids the calculations of seventy-five numerical coefficients. Secondly, by using a more accurate expression of the hard-sphere radial distribution function (HS-RDF), gHS(r), the accuracy of the analytical expression of the free energy second-order term is improved, being in agreement with its BH-MCA numerical evaluation. For short-range triangular-well potentials, the present EOS also leads to second-order residual internal energies and reduced pressures in better agreement with the molecular simulations than the Betancourt-Cárdenas et al. results.