Can a half-metallic zincblende-type structure be stabilized via epitaxy?

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The need for spin-injectors having the same zincblende-type crystal structure as conventional semiconductor substrates has created significant interests in theoretical predictions of possible metastable ``half-metallic'' zincblende ferromagnets, which are normally more stable in other structure-types, e.g., NiAs. Such predictions were based in the past on differences Δ bulk in the total-energies of the respective bulk crystal forms (zincblende and NiAs). We show here that the appropriate criterion is comparing difference Δ epi(aₛ) in epitaxial total-energies. This reveals that even if Δ bulk is small, still for MnAs, CrSb, CrAs, CrTe, Δ epi(aₛ) > 0 for all substrate lattice constant aₛ, so the zincblende phase is not stabilized. For CrS we find Δ epi(aₛ) <0, but the system is antiferromagnetic, thus not half-metallic. Finally, zincblende CrSe is predicted to be epitaxially stable for aₛ > 6.2 Å and half-metallic.