Point defects of intermetallic compounds B2 Nickel–based: DFT calculations

Abstract

This work utilizes Density Functional Theory (DFT) to examine the impact of point defects on non-stoichiometric B2 Nickel-based alloys. The investigation uses a Special Quasirandom Structure (SQS) to analyze random pseudo-binary A_1-xB_xC alloys of B2 NiGa, B2 NiZn and B2 NiBe with x values of 0.5 and 0.25. Our calculations confirm that Ni vacancies and Ni antisites are the primary point defects in Ga-rich and Ni-rich compositions of B2 NiGa, respectively. Ni antisites refer to the constitutional point defects found in the Ni-rich side of both B2 NiZn and B2 NiBe. On the other hand, Zn antisites and Be antisites are the constitutional defects found in the Zn-rich and Be-rich sides of B2 NiZn and B2 NiBe, respectively. We utilized the statistical-mechanical Wagner-Schottky model to forecast thermal defect concentrations at finite temperatures. This model relies on the enthalpies of production of point defects, which were determined using the SQS technique. Our results suggest that the primary thermal defects in B2 NiGa are of the triple-Ni defect type, and in B2 NiZn and B2 NiBe, they are of the Schottky type. Our calculated results are consistent with both experimental and theoretical findings.