Pair correlation function of short-ranged square-well fluids

TL;DR

This study uses Monte Carlo simulations to analyze the pair correlation function of square-well fluids with varying well widths, densities, and temperatures, and compares the results with two analytical theories to evaluate their predictive accuracy.

Contribution

It provides extensive simulation data for square-well fluids across different parameters and assesses the performance of two analytical theories in predicting their structure.

Findings

Both theories complement each other in predicting fluid structure.

The non-perturbative model performs well for short ranges and moderate densities.

The perturbation theory is more accurate for long ranges and high densities.

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 $\lambda-1$ ranging from 0.1 to 1.0, in units of the diameter $\sigma$ of the particles. For each one of these widths, several densities $\rho$ and temperatures $T$ in the ranges $0.1\leq\rho\sigma^3\leq 0.8$ and $T_c(\lambda)\lesssim T\lesssim 3T_c(\lambda)$, where $T_c(\lambda)$ 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.