We show that a structural energy difference, $\Delta E,$ must include explicit symmetry-breaking changes of the electronic structure due to temperature-induced configurational excitations, and why $\Delta E$ at $T=0\mathrm{}\hspace{0.5em}\mathrm{K}$ is not necessarily relevant to thermodynamic and mechanical modeling. In ${\mathrm{Ni}}_3\mathrm{V},$ we calculate a tenfold decrease of $\Delta E$ between ${D0\mathrm{}}_{22}$ and ${L1\mathrm{}}_2$ structures from $T=0\mathrm{}\hspace{0.5em}\mathrm{K}$ to states of order relevant to experiment. $\Delta E$ calculated directly from states with short-range order (8 meV) or with low partial order (7–12 meV) agree with high-T experiment (10 meV).

• Received 15 August 2000

DOI:https://doi.org/10.1103/PhysRevB.62.R11917