Phase stability of Au-Li binary systems studied using neural network potential

TL;DR

This study develops a neural network potential for Au-Li systems to accurately predict phase stability, revealing new stable phases and elucidating alloying mechanisms relevant for battery applications.

Contribution

We constructed an efficient neural network potential for Au-Li systems based on DFT data, enabling detailed phase stability analysis and discovery of a new stable phase.

Findings

Identified various compositions near the convex hull, explaining previous phase stability discrepancies.

Discovered a new stable phase Au0.469Li0.531 not reported before.

Demonstrated alloying process starting from phase separation to complete mixing.

Abstract

The miscibility of Au and Li exhibits a potential application as an adhesion layer and electrode material in secondary batteries. Here, to explore alloying properties, we constructed a neural network potential (NNP) of Au-Li binary systems based on density functional theory (DFT) calculations. To accelerate construction of NNPs, we proposed an efficient and inexpensive method of structural dataset generation. The predictions by the constructed NNP on lattice parameters and phonon properties agree well with those obtained by DFT calculations. We also investigated the mixing energy of Au$_{1-x}$Li$_{x}$ with fine composition grids, showing excellent agreement with DFT verifications. We found the existence of various compositions with structures on and slightly above the convex hull, which can explain the lack of consensus on the Au-Li stable phases in previous studies. Moreover, we newly found Au$_{0.469}$Li$_{0.531}$ as a stable phase, which has never been reported elsewhere. Finally, we examined the alloying process starting from the phase separated structure to the complete mixing phase. We found that when multiple adjacent Au atoms dissolved into Li, the alloying of the entire Au/Li interface started from the dissolved region. This paper demonstrates the applicability of NNPs toward miscible phases and provides the understanding of the alloying mechanism.