THEORETICAL-STUDY OF THE HIGH-PRESSURE PHASE-STABILITY OF GAP, INP, AND INAS

We report a first-principles study of the high-pressure structural pro perties and phase diagrams of GaP, InP, and InAs. The present study in cludes the Cmcm phase, which is a distortion of the rocksalt structure , and the lmm2 and sc16 phases, which have been suggested as stable hi gh pressure phases of III-V compounds. Our work relates directly to re cent experimental work on III-V compounds, which has indicated that th e previously reported high-pressure phase diagrams of these compounds should be reconsidered. Our results support the existence of stable Cm cm 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 a lso find a small range of thermodynamic stability for sc16 GaP. The en ergy-volume curves and phase diagrams of InP and InAs, as well as thos e of GaP and GaAs, show remarkable similarities. Along with previous w ork, we now have enough theoretical results to support a different sys tematics of the high-pressure phases of III-V compounds.