Thermodynamic Properties of Model Solids with Short-Ranged Potentials from Monte Carlo Simulations and Perturbation Theory

Monte Carlo simulations have been performed to determine the excess energy and the equation of state of fcc solids with Sutherland potentials for wide ranges of temperatures, densities, and effective potential ranges. The same quantities have been determined within a perturbative scheme by means of two procedures:  (i) Monte Carlo simulations performed on the reference hard-sphere system and (ii) second-order Barker−Henderson perturbation theory. The aim was twofold:  on the one hand, to test the capability of the “exact” MC-perturbation theory of reproducing the direct MC simulations and, on the other hand, the reliability of the Barker−Henderson perturbation theory, as compared with direct MC simulations and MC-perturbation theory, to determine the thermodynamic properties of these solids depending on temperature, density, and potential range. We have found that the simulation data for the excess energy obtained from the two procedures are in close agreement with each other. For the equation of state, the results from the MC-perturbation procedure also agree well with the direct MC simulations except for very low temperatures and extremely short-ranged potentials. Regarding the Barker−Henderson perturbation theory, we have found that in general the second-order approximation does not provide significant improvement over the first-order one.