Theoretical study of the high-pressure phase stability of GaP, InP, and InAs

We report a first-principles study of the high-pressure structural properties and phase diagrams of GaP, InP, and InAs. The present study includes the Cmcm phase, which is a distortion of the rocksalt structure, and the Imm2 and sc16 phases, which have been suggested as stable high-pressure phases of III-V compounds. Our work relates directly to recent experimental work on III-V compounds, which has indicated that the previously reported high-pressure phase diagrams of these compounds should be reconsidered. Our results support the existence of stable Cmcm phases in InP and InAs and a stable or nearly stable Cmcm phase in GaP. We find stable Imm2 phases in each of the compounds studied. We also find a small range of thermodynamic stability for sc16 GaP. The energy-volume curves and phase diagrams of InP and InAs, as well as those of GaP and GaAs, show remarkable similarities. Along with previous work, we now have enough theoretical results to support a different systematics of the high-pressure phases of III-V compounds.