An-Najah Staff

FP-LAPW CALCULATIONS OF THE STRUCTURAL PHASE TRANSFORMATIONS OF ZnSe AND ZnS UNDER HIGH PRESSURE At present, calculations of ground–state energy of II–VI and III–V compounds are computed relatively slowly and expensively, even on supercomputers. Thus, an efficient, inexpensive and accurate method of calculations is very important. The Full-Potential Linearized Augmented Plane-Wave (FP-LAPW) method have been used to investigate the structural phase transformations of ZnS and ZnSe under high-pressure. In these calculations, the local density approximation (LDA) for the exchange-correlation potential have been used. Equations of states (EOS's) of the zinc-blende (ZB), rock-salt (RS), cinnabar and simple cubic-16 (SC16) of the ZnS and ZnSe have been calculated. From these EOS's, the structural phase transformations of both ZnS and ZnSe under high pressure were investigated by treating the 3d-electrons of Zn and Se as valence states. Moreover, the structural properties and the electronic structures of the ZB, RS, cinnabar and SC16 phases of ZnS and ZnSe have also been calculated. The most important results are:(1) our calculations agree very well with the available experimental data and the other theoretical calculations. (2) the relaxation of the internal parameters of the (ZnS and ZnSe) in cinnabar and SC16 structures have important effects on its calculated equation of state. (3) the ZB and RS forms of ZnS are found to be semiconductors up to the transition pressure. (4) the ZB form of ZnSe is found to be semiconductor while the RS of ZnSe is found to be semimetal with narrow energy band-gap of 0.5eV. (5) the cinnabar and SC16 structures of ZnS and ZnSe which lies between ZB and RS are expected to be semiconductors. (6) SC16 is a stable phase and relatively more stable than RS and cinnabar phases for ZnS and ZnSe.