Comparing four hard-sphere approximations for the low-temperature WCA melting line

TL;DR

This study compares four hard-sphere approximations for predicting the low-temperature melting line of the WCA system, using simulations and thermodynamic integration to evaluate their accuracy.

Contribution

It provides a detailed comparison of four theoretical approximations against simulation data for the WCA melting line, highlighting the most accurate models.

Findings

Andersen-Weeks-Chandler and Barker-Henderson approximations are most accurate.

Both accurate in the zero-temperature limit with derived analytical expressions.

Simulation data covers four decades of temperature.

Abstract

By combining interface-pinning simulations with numerical integration of the Clausius-Clapeyron equation we determine accurately the melting-line coexistence pressure and fluid/crystal densities of the Weeks-Chandler-Andersen (WCA) system covering four decades of temperature. The data are used for comparing the melting-line predictions of the Boltzmann, Andersen-Weeks-Chandler, Barker-Henderson, and Stillinger hard-sphere approximations. The Andersen-Weeks-Chandler and the Barker-Henderson theories give the most accurate predictions, and they both work excellently in the zero-temperature limit for which analytical expressions are derived here.