The square-well potential has been one of the most used to derive properties for real fluids since it qualitatively represents the basic part of the interaction between molecules. This potential has a short repulsive interaction and a constant attractive well of finite range. Perturbation theory of Barker and Henderson [1] can be used to represent the properties of this fluid, and this has been used for well ranges usually less than twice the hard sphere diameter. The long-ranged square-well potential (well ranges greater than twice the hard sphere diameter) has not been widely studied even though its behavior can be used to represent long-range interactions, such as those of polar molecules. In this work, the perturbation series of Barker and Henderson [1] for the long-ranged square-well potential has been evaluated by molecular simulation and the convergence of the series is examined by considering the vapor-liquid coexistence curve.

[1] J.A. Barker, D. Henderson, Rev. Mod. Phys. 48 (1976) 587-671.