Pair correlation function of short-ranged square-well fluids

Abstract

We have performed extensive Monte Carlo simulations in the canonical (NVT) ensemble of the pair correlation function for square-well fluids with well widths $λ-1$ ranging from 0.1 to 1.0, in units of the diameter $σ$ of the particles. For each one of these widths, several densities $ρ$ and temperatures $T$ in the ranges $0.1\leqρσ^3\leq 0.8$ and $T_c(λ)\lesssim T\lesssim 3T_c(λ)$, where $T_c(λ)$ is the critical temperature, have been considered. The simulation data are used to examine the performance of two analytical theories in predicting the structure of these fluids: the perturbation theory proposed by Tang and Lu [Y. Tang and B. C.-Y. Lu, J. Chem. Phys. {\bf 100}, 3079, 6665 (1994)] and the non-perturbative model proposed by two of us [S. B. Yuste and A. Santos, J. Chem. Phys. {\bf 101}, 2355 (1994)]. It is observed that both theories complement each other, as the latter theory works well for short ranges and/or moderate densities, while the former theory does for long ranges and high densities.