Discrete perturbation theory for the hard-core attractive and repulsive Yukawa potentials

摘要

In this work we apply the discrete perturbation theory [A. L. Benavides and A. Gil-Villegas, Mol.Phys. 97, 1225 (1999)] to obtain an equation of state for the case of two continuous potentials: thehard-core attractive Yukawa potential and the hard-core repulsive Yukawa potential. The main advantage of the presented equation of state is that it is an explicit analytical expression in theparameters that characterize the intermolecular interactions. With a suitable choice of their inverse screening length parameter one can model the behavior of different systems. This feature allows usto make a systematic study of the effect of the variation in the parameters on the thermodynamic properties of this system. We analyze single phase properties at different conditions of density andtemperature, and vapor-liquid phase diagrams for several values of the reduced inverse screening length parameter within the interval κ~*=0.1-5.0. The theoretical predictions are compared withavailable and new Monte Carlo simulation data. Good agreement is found for most of the cases and better predictions are found for the long-range ones. The Yukawa potential is an example of a familyof hard-core plus a tail (attractive or repulsive) function that asymptotically goes to zero as the separations between particles increase. We would expect that similar results could be found for otherpotentials with these characteristics.