The equilibrium vacancy concentration in multi-principal element alloys remains a controversial and nontrivial subject, primarily because of chemical complexity and chemical short-range order (CSRO). Here we derive an exact expression that is amenable to atomistic calculations, using multiple perspectives. We applied this expression to equiatomic CrCoNi alloys in the face-centered cubic structure. The derived equilibrium vacancy concentration is used in our recent work, which predicts the chemical short-range order formation timescale consistent with experimental observation. The results demonstrate the practical utility of the approach for predicting equilibrium vacancy concentrations in compositionally complex alloys.
@article{arxiv.2512.22370,
title = {Thermal Equilibrium Vacancy Concentration in an Alloy with Chemical Short-Range Order},
author = {Hao Tang and Hoje Chun and Rafael Gomez-Bombarelli and Yuri Mishin and Ju Li},
journal= {arXiv preprint arXiv:2512.22370},
year = {2025}
}