First-principles study on local site preference of interstitial oxygen in Ti3Zr1.5NbVAl0.25 high-entropy alloy

The occupancy of interstitial oxygen atoms in high-entropy alloy exhibits site preferences, thus affecting alloy properties. In this work, first-principles calculations were employed to investigate the physical origin of the local site preference of oxygen in Ti₃Zr_1.5NbVAl_0.25 high-entropy alloy. The results indicate that the formation energies are closely correlated with the coordinating atoms in the interstitial environment. Interstitial oxygen tends to occupy the coordination environment of Ti and Zr, which is not conducive to stabilizing the Al coordination environment. Such local site preference primarily depends on the amount of charge transfer and lattice distortion, which encourages interstitial oxygen to occupy Ti and Zr-rich environments. Conversely, minimal charge transfer between Al and oxygen hinders the solid solution of interstitial oxygen. The present work thus offers insights and theoretical guidance for the design of high-performance lightweight refractory high-entropy alloys.