${\mathrm{Ga}}_{0.5}$${\mathrm{In}}_{0.5}$P alloys order spontaneously during growth into a (111) monolayer superlattice despite the fact that this is not the lowest-energy structure of the three-dimensional bulk compound. Using first-principles total-energy calculations, we show that a novel electronically driven surface reconstruction provides a driving force for such ordering.

• Received 26 November 1990

DOI:https://doi.org/10.1103/PhysRevLett.66.2132