Identifying The Transition State in Structurally Unstable but Dynamically Stabilized Phases: A GPR-Assisted First Principles Methodology

Numerous materials of technological importance feature high-temperature phases that exhibit phonon instabilities. Leading examples include shape-memory alloys, ferroelectric and refractory oxides, and some metal hydrides. I will introduce a new model for diffusion barrier calculation in these phases. Our model efficiently explores the system’s diffusive transition path using the dimer scheme based on a Gaussian process regression (GPR) of the temperature-dependent energy surface. Our model simultaneously samples the temperature-dependent energy surface and converges the system towards the saddle point. Our method provides a useful alternative to methods such as molecular dynamics, which directly simulate diffusive hops. I present the application of this model for some example metals and oxides.<br/><br/>References<br/>S. Kadkhodaei and A. Davariashtiyani, Phys. Rev. Materials 4, 043802, 2020<br/>Fattahpour, S and Davariashtiyani, A and Kadkhodaei, S. Phys. Rev. Materials 6, 023803, 2022