Site preference of ternary alloying elements in Ni₃Al: A first-principles study

First-principles supercell calculations were performed to predict the site preference of Pt, Hf, Cr and Ir in L1₂ Ni₃Al. Our calculations showed that, at T = 0 K, Pt always prefers Ni sites, while Cr and Hf always prefer Al sites in Ni₃Al. The site preference of Ir was found to be strongly composition-dependent: Ir prefers Ni sites in Al-rich and Al sites in Ni-rich Ni₃Al, and shows no site preference in stoichiometric Ni₃Al. The effects of temperature on site preference of ternary alloying elements were further studied using a statistical-mechanical Wagner-Schottky model in combination with our first-principles calculated point defect formation enthalpies. Our calculations showed that the site preference of Ir is also strongly affected by temperature.