The temperature-composition phase diagrams of the pseudoternary (${\mathrm{CuInSe}}_2$${)}_{1\mathrm{-}\mathit{x}}$(ZnSe${)}_{2\mathit{x}}$ and (${\mathrm{ZnSnP}}_2$${)}_{1\mathrm{-}\mathit{x}}$(GaP${)}_{2\mathit{x}}$ chalcopyrite–zinc-blende semiconducting alloys are obtained by a combination of first-principles total-energy calculations with a statistical-mechanics description of a spin-1 Hamiltonian. We find that (i) alloying with zinc blende sharply lowers the order-disorder transition temperature of the chalcopyrite, (ii) despite the different crystal structures of the constituents, the alloy exhibits miscibility already above ∼500 K, and (iii) while the equilibrium ground state corresponds to phase separation, a metastable long-range-ordered intermediate stannite-type compound ${\mathrm{CuInZn}}_2$${\mathrm{Se}}_4$ is predicted.

• Received 19 October 1992

DOI:https://doi.org/10.1103/PhysRevB.47.9985