Lattice-switch Monte Carlo: the fcc-bcc problem

TL;DR

This paper introduces lattice-switch Monte Carlo for calculating free energy differences between solid phases, applies it to fcc and bcc phases in Lennard-Jones systems, and discusses challenges with the bcc phase's stability.

Contribution

The paper presents a lattice switch method based on the Bain orientation for fcc-bcc phase transitions and highlights stability issues in the bcc phase.

Findings

bcc phase is unstable and degenerates into metastable phases

conventional lattice-switch Monte Carlo is intractable for bcc

discusses potential solutions to stability problems

Abstract

Lattice-switch Monte Carlo is an efficient method for calculating the free energy difference between two solid phases, or a solid and a fluid phase. Here, we provide a brief introduction to the method, and list its applications since its inception. We then describe a lattice switch for the fcc and bcc phases based on the Bain orientation relationship. Finally, we present preliminary results regarding our application of the method to the fcc and bcc phases in the Lennard-Jones system. Our initial calculations reveal that the bcc phase is unstable, quickly degenerating into some as yet undetermined metastable solid phase. This renders conventional lattice-switch Monte Carlo intractable for this phase. Possible solutions to this problem are discussed.