$\textit{Ab initio}$ construction of full phase diagram of MgO-CaO eutectic system using neural network interatomic potentials

TL;DR

This study demonstrates that neural network interatomic potentials can efficiently and accurately construct a full phase diagram of the MgO-CaO system, closely matching experimental data and significantly reducing computational cost.

Contribution

The paper introduces a method using neural network potentials trained on DFT data to construct complete phase diagrams of multi-component systems, including liquid phases, with high accuracy and efficiency.

Findings

The neural network potential accurately reproduces the MgO-CaO phase diagram features.

The approach is over 1,000 times faster than traditional DFT methods.

The SCAN functional-based NNP closely matches experimental phase boundaries.

Abstract

While several studies confirmed that machine-learned potentials (MLPs) can provide accurate free energies for determining phase stabilities, the abilities of MLPs for efficiently constructing a full phase diagram of multi-component systems are yet to be established. In this work, by employing neural network interatomic potentials (NNPs), we demonstrate construction of the MgO-CaO eutectic phase diagram with temperatures up to 3400 K, which includes liquid phases. The NNP is trained over trajectories of various solid and liquid phases at several compositions that are calculated within the density functional theory (DFT). For the exchange-correlation energy among electrons, we compare the PBE and SCAN functionals. The phase boundaries such as solidus, solvus, and liquidus are determined by free-energy calculations based on the thermodynamic integration or semigrand ensemble methods, and salient features in the phase diagram such as solubility limit and eutectic points are well reproduced. In particular, the phase diagram produced by the SCAN-NNP closely follows the experimental data, exhibiting both eutectic composition and temperature within the measurements. On a rough estimate, the whole procedure is more than 1,000 times faster than pure-DFT based approaches. We believe that this work paves the way to fully $\textit{ab initio}$ calculation of phase diagrams.