Surface composition of ordered alloys:  An off-stoichiometric effect

I predict the existence of an off-stoichiometric effect in ordered alloys in the form of a distinct transition in the surface segregation behavior of alloy components near the bulk stoichiometric composition. It is caused by the discontinuity in the effective chemical potential at the stoichiometric composition. The effect is predicted to occur at the (111) surface of ordered ${\mathrm{Ni}}_3\mathrm{Al}$ and ${\mathrm{Pt}}_3\mathrm{Fe}$ alloys.