Long- versus short-range order in Ni3V and Pd3V alloys

Measurements of the short-range-order (SRO) diffuse scattered intensity show peaks at the 11/20 and 100 points in Ni3V and Pd3V, respectively, although the stable ground state in both systems (D022) is a 11/20-type structure. Mean-field theory predicts 11/20 SRO in both materials, in contradiction with experiment for Pd3V. The 100-type SRO in Pd3V has been explained previously as a non-mean-field effect. Via a combination of first-principles total-energy calculations and Monte Carlo simulated annealing, we show that non-mean-field effects are insufficient to explain the observed SRO of Pd3V. However, the inclusion of electronic excitations leads to a temperature dependence in the interaction energies which correctly explains both the SRO and phase stability in Pd3V and Ni3V.