Determinants of vacancy formation and migration in high-entropy alloys

Abstract

Vacancies are crucial for the radiation resistance, strength, and ductility of high-entropy alloys (HEAs). However, complex electronic interactions resulting from chemical disorder prohibit the quantification of vacancy formation energy (<i>E</i>_f) and migration barriers (<i>E</i>_b). Herein, we propose an electronic descriptor χ<i>S</i>_v (electronegativity χ and valence-electron number <i>S</i>_v) to quantify the bonding strength of constituents on the basis of the tight-binding model, which allows us to build analytical models to achieve the site-to-site quantification of <i>E</i>_f and <i>E</i>_b. The descriptor χ<i>S</i>_v reflects the d-band occupation, indicating the dominant role of the electronic interactions in the vacancy formation and migration of HEAs. As a size effect, local lattice distortion plays a more important role in vacancy migration than in vacancy formation. Our model establishes a universal physical picture of vacancy formation and migration, which helps to understand the radiation resistance and mechanical properties of HEAs, thereby accelerating the design of high-performance HEAs.