Accurate prediction of vacancy cluster structures and energetics in bcc transition metals

Abstract Knowledge on structures and energetics of vacancy clusters is fundamental to understand defect evolution in metals. Yet there remain no reliable methods able to determine essential structural details or to provide accurate assessment of energetics for general vacancy clusters. Here, we performed systematic first-principles investigations to examine stable structures and energetics of vacancy clusters in bcc metals, explicitly demonstrated the stable structures can be precisely determined by minimizing their Wigner-Seitz area, and revealed a linear relationship between formation energy and Wigner-Seitz area of vacancy clusters. We further developed a new physics-based model to accurately predict stable structures and energetics for arbitrary-sized vacancy clusters. This model was well validated by first-principles calculations and recent vacancy cluster annealing experiments, and showed distinct advantages over the widely used spherical approximation. The present work offers mechanistic insights that crucial for understanding vacancy cluster formation and evolution, provides crucial benchmarks for assessing empirical interatomic potentials, and enables a critical step towards predictive control and prevention of vacancy cluster related damage processes in structural metals.