On the performance of interatomic potential models of iron: comparison of the phase diagrams

TL;DR

This study compares four embedded-atom potential models of iron to evaluate their accuracy in predicting phase diagrams across a wide pressure range, highlighting the importance of fitting procedures for reliable high-pressure predictions.

Contribution

It provides a systematic comparison of interatomic potential models for iron's phase behavior under high pressure using nested sampling.

Findings

All models predict bcc as stable at low pressure.

Significant variation in high-pressure phases among models.

The model fitted with liquid properties aligns well with experimental data.

Abstract

In order to study the performance of interatomic potentials and their reliability at higher pressures, the phase diagram of four different embedded-atom type potential models of iron is compared. The calculations were done by the nested sampling technique in the pressure range 0.1 GPa-100 GPa. The low pressure stable structure is found to be the body- centred cubic in all cases, but the higher pressure phases show a great variation, being face-centred cubic, hexagonal close-packed and - at very low temperatures - different body-centred tetragonal phases are observed as well. The melting line is overestimated considerably for three of the models, but for the one where liquid properties had been taken into account during the potential fitting process, the agreement with experimental results is good, even at very high pressures.