Defect structures and ternary lattice site preference of the B2 phase in the Al-Ni-Ru system

The energies for stoichiometric and defected binary and ternary B2 phases in the Al-Ni-Ru ternary system were calculated from first-principles. The dominant compositions-conserving constitutional defect structures for NiAl and RuAl have been determined as (Al, Ni)(Ni, Va) and (Ru, Al, Va)(Al), respectively. It was observed that Ru prefers the Ni-sublattice in NiAl, while Ni has a very strong preference for the Ru-sublattice in RuAl. Furthermore, the results indicate that a miscibility gap is likely to be stable at low temperatures in the NiAl-RuAl pseudobinary system.