Phase Stability and Site Substitution in NB-AL Compounds

Abstract

AbstractThe site preferences of Ta, Mo, and W in A15 Nb3Al, the phase stability of off-stoichiometric A15 Nb3Al, and the atomic order of the Nb2Al D8b (σ) phase are investigated by performing electronic structure calculations based on the local density approximation. Mo, W, and Ta are found to have a preference for the Nb sublattice. Ta has the strongest site preference. It was shown that some recently proposed ground states for off-stoichiometric A15 phases are unlikely to occur in the Nb-Al system. Moreover, it was shown that the atomic order in the D8b Nb2Al phase contributes significantly to its stability.