Long- versus short-range order inNi3V andPd3V alloys

Measurements of the short-range-order (SRO) diffuse scattered intensity show peaks at the 〈11/20〉 and 〈100〉 points in ${\mathrm{Ni}}_3$V and ${\mathrm{Pd}}_3$V, respectively, although the stable ground state in both systems (D$0_{22}$) is a 〈11/20〉-type structure. Mean-field theory predicts 〈11/20〉 SRO in both materials, in contradiction with experiment for ${\mathrm{Pd}}_3$V. The 〈100〉-type SRO in ${\mathrm{Pd}}_3$V 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 ${\mathrm{Pd}}_3$V. 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 ${\mathrm{Pd}}_3$V and ${\mathrm{Ni}}_3$V.