Lennard-Jones systems near solid walls: Computing interfacial free energies from molecular simulation methods

TL;DR

This study employs multiple molecular simulation techniques to compute interfacial free energies of Lennard-Jones systems near solid walls, analyzing effects of wall structure, density, and temperature on wetting behavior.

Contribution

It introduces a comprehensive comparison of computational methods for interfacial free energies and explores how wall structure and interaction parameters influence wetting phenomena.

Findings

Interfacial free energies vary with density and temperature.

Structured walls affect the contact angle and wetting behavior.

Multiple methods yield consistent interfacial energy estimates.

Abstract

Different computational techniques in combination with molecular dynamics computer simulation are used to to determine the wall-liquid and the wall-crystal interfacial free energies of a modified Lennard-Jones (LJ) system in contact with a solid wall. Two different kinds of solid walls are considered: a flat structureless wall and a structured wall consisting of an ideal crystal with the particles rigidly attached to fcc lattice sites. Interfacial free energies are determined by a thermodynamic integration scheme, the anisotropy of the pressure tensor, the non-equilibrium work method based on Bennett acceptance criteria, and a method using Cahn's adsorption equations based on the interfacial thermodynamics of Gibbs. For the flat wall, interfacial free energies as a function of different densities of the LJ liquid and as a function of temperature along the coexistence curve are calculated. In case of a structured wall, the interaction strength between the wall and the LJ system and the lattice constant of the structured wall are varied. Using the values of the wall-liquid and wall-crystal interfacial energies along with the value for the crystal-liquid interfacial free energy determined previously for the same system by the "cleaving potential method", we obtain the contact angle as a function of various parameters; in particular the conditions are found under which partial wetting occurs.