Exploring the mechanism of phase transitions between the hexagonal close-packed and the cuboidal structures

TL;DR

This paper investigates the phase transition mechanisms between hcp, fcc, and bcc structures using lattice parameter mapping and energy path analysis across different models, clarifying the role of fcc as an intermediate phase.

Contribution

It introduces a method to map minimum energy paths between lattice structures and demonstrates that fcc acts as an intermediate phase in phase transitions for multiple models.

Findings

Direct hcp to fcc transition observed in all models.

f c c serves as an intermediate phase in the transition.

The transition pathways are consistent across different models.

Abstract

By introducing appropriate lattice parameters for a bi-lattice smoothly connecting the hexagonal close-packed (hcp) with the cuboidal structures, namely the body-centered (bcc) and the face centered cubic (fcc) lattices, we were able to map out the minimum energy path for a Burgers-Bain type of phase transition. We demonstrate that for three different models applied, i.e. the kissing hard-sphere model, the Lennard-Jones potential, and density functional theory for metallic lithium, the direct transition path is always from hcp to fcc with a separate path leading from fcc to bcc. This solves, at least for the models considered here, a long-standing controversy of whether or not fcc acts as an intermediate phase in martensitic type of phase transitions.