Liquid-vapor coexistence in square-well fluids: an RHNC study

TL;DR

This study evaluates the reference hypernetted-chain integral equation's effectiveness in predicting the liquid-vapor phase diagram of square-well fluids, demonstrating good accuracy with an extrapolation method across different attraction ranges.

Contribution

It shows that the RHNC integral equation, combined with an extrapolation technique, can reliably estimate phase diagrams of square-well fluids, aiding quick assessments and complex anisotropic molecule studies.

Findings

RHNC reproduces coexistence curves with good accuracy

Extrapolation mitigates pseudo-spinodal pathologies

Method aids in studying anisotropic patchy molecules

Abstract

We investigate the ability of the reference hypernetted-chain integral equation to describe the phase diagram of square-well fluids with four different ranges of attraction. Comparison of our results with simulation data shows that the theory is able to reproduce with fairly good accuracy a significant part of the coexistence curve, provided an extrapolation procedure is used to circumvent the well-known pathologies of the pseudo-spinodal line, which are more severe at reduced width of the attractive well. The method provides a useful approach for a quick assessment of the location of the liquid-vapor coexistence curve in this kind of fluid and serves as a check for the more complex problem of anisotropic "patchy" square-well molecules.