Synthesis challenges, thermodynamic stability, and growth kinetics of La–Si–P ternary compounds

Abstract

Although many new compounds have been recently predicted with the help of machine learning, the successful experimental synthesis of these compounds remains challenging. Computational insights about the thermodynamic stability and phase formation kinetics among the ground state and competing metastable phases are highly desirable to rationalize and attempt to overcome synthesis challenges experimentally. In this work, we explore synthetic challenges within ternary La–Si–P compounds through feedback between experimental and computational studies. We discuss the experimental challenges in forming three computationally predicted ternary phases (La₂SiP, La₅SiP₃, and La₂SiP₃). To understand the synthetic challenges, we performed molecular dynamics (MD) simulations using an accurate and efficient artificial neural network machine learning (ANN-ML) interatomic potential. We study the phase stability and formation kinetics of these ternary phases in relation to the reported and synthesized La₂SiP₄ phase. While the growth of the La₂SiP₄ phase can be reproduced by our MD simulation, our results indicate that the rapid formation of a Si-substituted LaP crystalline phase is a major barrier to the synthesis of the predicted La₂SiP, La₅SiP₃, and La₂SiP₃ ternary compounds, agreeing well with experimental observations. Our simulations also suggest that there is a narrow temperature window in which the La₂SiP₃ phase can be grown from the solid–liquid interface.