Density functional theory of inhomogeneous liquids. I. The liquid-vapor interface in Lennard-Jones fluids

TL;DR

This paper introduces a simplified density functional theory model for inhomogeneous Lennard-Jones fluids, accurately predicting the liquid-vapor interface properties by using only the homogeneous fluid's free energy as input.

Contribution

The paper presents a new, simplified model for the direct correlation function that effectively predicts interfacial properties of Lennard-Jones fluids using minimal input.

Findings

Model accurately predicts surface tension in good agreement with simulations.

Simplified approach reduces computational complexity.

Effective for a wide range of densities.

Abstract

A simple model is proposed for the direct correlation function (DCF) for simple fluids consisting of a hard-core contribution, a simple parametrized core correction, and a mean-field tail. The model requires as input only the free energy of the homogeneous fluid, obtained, e.g., from thermodynamic perturbation theory. Comparison to the DCF obtained from simulation of a Lennard-Jones fluid shows this to be a surprisingly good approximation for a wide range of densities. The model is used to construct a density functional theory for inhomogeneous fluids which is applied to the problem of calculating the surface tension of the liquid-vapor interface. The numerical values found are in good agreement with simulation.