Unified Model for the Solution of Interstitials in Refractory High-Entropy Alloys

The solution of interstitial nonmetallic solutes (INSs) like H, He, O, C, N, P, and S is common in refractory high-entropy alloys (RHEAs) and essentially controls the RHEAs properties. However, the disorder local chemical environments of RHEAs hinder the quantitative prediction of the stability of INSs and the understanding of the underlying mechanism. Based on the tight-binding models, we propose an analytic model for determining the solution energy of INSs in RHEAs. This predictive model identifies that the energetics of INSs depends linearly on the d-band width of their neighbors, with the slope determined by the bonding characteristics of INSs. Our scheme provides an electronic-level understanding of INSs in RHEAs and explains key experimental observations, which can serve as an effective tool for designing advanced RHEAs.