Solid solution formation and electronic structure investigation of NbNiZrTiCo high-entropy alloys using first-principles calculations

Abstract

The solid-solution formation and electronic structure of the NbNiZrTiCo high-entropy alloy (HEA) were investigated using first-principles density functional theory (DFT). Multiple supercell sizes with randomized atomic configurations were used to assess the stability in both hcp and bcc structures. The configurational entropy, expressed through the Ω parameter, increases with supercell size and satisfies the solid-solution stability criterion. This entropy-driven stabilization compensates for lattice distortion caused by atomic size mismatch, quantified by δ. Because the valence electron concentration (VEC) conditions are semi-empirical, it does not clearly determine the preferred structure. However, the satisfied Ω criterion suggests that both hcp and bcc structures are stable, in agreement with experimental observations. Electronic structure analysis further reveals that the charge transfer behavior is consistent with the electronegativities of the constituent elements.