  Knowledge on structures and energetics of nanovoids 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 nanovoids. Here, we performed systematic
first-principles investigations to examine stable structures and energetics of
nanovoids 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
nanovoids. We further developed a new physics-based model to accurately predict
stable structures and energetics for arbitrary-sized nanovoids. This model was
well validated by first-principles calculations and recent nanovoid annealing
experiments, and showed distinct advantages over the widely used spherical
approximation. The present work offers mechanistic insights that crucial for
understanding nanovoid formation and evolution, being a critical step towards
predictive control and prevention of nanovoid related damage processes in
structural metals.
