Metadynamics for Vacancy Dynamics in Crystals

TL;DR

This paper introduces a novel metadynamics-based method for efficiently constructing the vacancy free energy surface in crystals without predefined vacancy coordinates, leveraging symmetry and parallel bias techniques.

Contribution

The proposed approach enables vacancy FES construction without explicit vacancy parameters, improving efficiency with a multi-hill symmetry-exploiting strategy.

Findings

Validated on self-diffusion and impurity diffusion in metallic and ionic crystals.

Achieved accurate vacancy FES without predefined vacancy coordinates.

Enhanced efficiency through parallel bias and multi-hill strategies.

Abstract

We propose a metadynamics-based (MetaD-based) approach for constructing the free energy surface (FES) of vacancy dynamics in crystals. In this approach, the vacancy FES can be constructed without explicitly defining a unique vacancy coordinate or introducing a set of parameters that strongly govern the FES topology, enabled by parallel bias MetaD with partitioned families (PB MetaDPF). In addition, the proposed approach is made more efficient and effective through a multi-hill strategy that exploits crystallographic symmetry. We demonstrate the validity of the proposed approach through applications to self-diffusion and impurity diffusion via monovacancies and divacancies in metallic and ionic crystals.