HIGH-PRESSURE STABILITY IN III-V AND II-VI BINARY COMPOUNDS AND THE CMCM PHASE - A THEORETICAL-STUDY

We present the results of a theoretical study based on the density fun ctional theory of the structural stability of several III-V and II-VI binary compounds (GaAs GaP, InAs, InP, ZnSe, and ZnTe, among others). The recent developments in X-ray diffraction techniques have led to th e identification of several new phases and to a major change in the ac cepted trends for these families of compounds. A remarkable feature of the emerging new picture is the existence of an orthorhombic phase wh ich is stable in many of the binary compounds studied so far, a distor tion of the rocksalt structure which hay been named Cmcm after its spa ce group. Our theoretical study focuses on this novel and rather gener al phase. We have investigated the instability of the rocksalt cell wi th respect to the distortion leading to Cmcm. The results of our ab in itio study are in line with recent experimental studies of these compo unds.