Free energy calculations for atomic solids through the Einstein crystal/molecule methodology using GROMACS and LAMMPS

TL;DR

This paper demonstrates how to compute free energies of atomic solids using Einstein crystal/molecule methods with GROMACS and LAMMPS, showing good agreement with Monte Carlo results and enabling routine calculations for isotropic potentials.

Contribution

It introduces a procedure for free energy calculations of solid phases in GROMACS and LAMMPS, expanding their application to atomic solids and colloidal particles.

Findings

Good agreement with Monte Carlo results

Routine free energy calculations for isotropic potentials

Method applicable to atomic and colloidal solids

Abstract

In this work the free energy of solid phases is computed for the Lennard-Jones potential and for a model of NaCl. The free energy is evaluated through the Einstein crystal/molecule methodologies using the Molecular Dynamics programs: GROMACS and LAMMPS. The obtained results are compared with the results obtained from Monte Carlo. Good agreement between the different programs and methodologies was found. The procedure to perform the free energy calculations for the solid phase in the Molecular Dynamic programs is described. Since these programs allow to study any continuous intermolecular potential (when given in a tabulated form) this work shows that for isotropic potentials (describing for instance atomic solids or colloidal particles) free energy calculations can be performed on a routinely basis using GROMACS and/or LAMMPS.