Thermal Equilibrium Vacancy Concentration in an Alloy with Chemical Short-Range Order

TL;DR

This paper derives an exact expression for equilibrium vacancy concentration in complex alloys with chemical short-range order, enabling accurate atomistic predictions and aligning with experimental observations.

Contribution

It introduces a novel exact formula for vacancy concentration in alloys with CSRO, applicable to atomistic calculations and complex compositions.

Findings

Derived an exact expression for vacancy concentration

Applied the formula to CrCoNi alloys

Predicted vacancy concentrations consistent with experiments

Abstract

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.