First-principles study of site occupancy of dilute 3d, 4d and 5d transition metal solutes in L1₀ TiAl

Using a statistical-mechanical Wagner-Schottky model parametrized by first-principles density-functional (DFT-GGA) calculations on 32-atom supercells, we predict the lattice site occupancy of 3d (Ti-Cu), 4d (Zr-Ag) and 5d (Hf-Au) transition-metal elements in L1₀ TiAl intermetallic compound as a function of both alloy composition and temperature. The effects of local atomic relaxations, anisotropic lattice distortions, as well as magnetism on point defect energetics are fully taken into account. Our calculations show that, at all alloy compositions and temperatures, Zr and Hf consistently show a preference for the Ti sublattice, while Co, Ru, Rh, Pd, Ag, Re, Os, Ir, Pt and Au consistently show a preference for the Al sublattice. In contrast, the site preference of V, Cr, Mn, Fe, Ni, Cu, Nb, Mo, Tc, Ta and W strongly depend on both alloy stoichiometry and temperature. Our calculated results compare favorably with the existing theoretical and experimental studies in the literature.