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The short-range order (SRO) and long-range order (LRO) of Ni-V and Pd-V alloys are studied theoretically by a combination of first-principles calculations of Ising-like interaction energies (J₅) with a Monte Carlo solution of the Ising Hamiltonian. We find the following: (i) There are several compositions in these alloys for which the dominant wave vectors of LRO and those of SRO do not coincide, indicating that the low-temperature (T) LRO may not always be inferred from the high-T SRO. (ii) In Ni₃V and Pd₃V, the density of states at the Fermi level, n (₅), is much larger in L1₂ than in the stable D0₂₂ structure. This has two consequences: (a) thermal electron-hole excitations across ₅ are energetically more favorable in the L1₂ structure and lead to a T dependence of J₅, and (b) magnetization stabilization is larger in L1₂, so spin polarization affects structural stability. As a result, (iii) calculations using T-dependent J₅'s are needed to obtain quantitative agreement with experimental measurements of LRO, SRO, and transition temperatures in Ni₀. ₇₅V₀. ₂₅, Ni₀. ₆₇V₀. ₃₃, and Pd₀. ₇₅V₀. ₂₅. (iv) We provide predictions of the SRO patterns where there is currently no experimental evidence for Pd₀. ₆₇V₀. ₃₃, Ni₀. ₆V₀. ₄, Pd₀. ₆V₀. ₄, and Pd₀. ₅V₀. ₅. (v) For Ni₃V and Pd₃V, discrepancies are found between the total-energy differences of the L1₂ and D0₂₂ structures as determined by T=0 first-principles calculations and those inferred from diffuse neutron scattering measurements at high T. By performing temperature-dependent self-consistent local-density-approximation calculations, we find that electronic excitations are responsible for reducing the discrepancy by 25% and the combination of spin polarization and electronic excitations reduce the discrepancy by 30--50 %. Thus, electronic excitations and spin polarization are not fully responsible for the T dependence of J₅ used in the SRO calculations.
Wolverton et al. (Fri,) studied this question.