Pressure-induced phase transition and metallization of solid ZnSe

We theoretically study the structural properties and pressure-induced solid–solid phase transitions of ZnSe by using the first-principles pseudopotential method. The zinc-blende (ZB), rock-salt (RS), cinnabar, cmcm, SC16 (simple cubic with 16-atom basis) phases of ZnSe have been considered. It has been shown that the cinnabar phase is not a stable phase in ZnSe under high pressure. The sequence of these phases is ZB → SC16 → RS → cmcm with transition pressure was found to be 13 GPa, 17 GPa and 29.8 GPa, respectively. It has been predicted that the ZB and SC16 phases are semiconductor characteristics with the direct band gaps 1.36 eV and 0.76 eV, respectively. Especially the band gap of the ZB structure increases with the pressure. The calculated metallization pressure is 17 GPa, is well consistent with the experimental results, and the metallization is caused by the phase transition from SC16 to RS structure, rather than as a result of the band closure.