Determinants of vacancy formation and migration in high-entropy alloys

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 (Ef) and migration barriers (Eb). Herein, we propose an electronic descriptor chi Sv (electronegativity chi and valence-electron number Sv) 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 Ef and Eb. The descriptor chi Sv 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.