Pressure-induced elemental dissociation in zinc chalcogenides

Abstract

We have extensively explored the high-pressure structures of zinc chalcogenides (ZnX, X = S, Se and Te) by using first-principles calculations. The previously assumed high-pressure CsCl phase was ruled out and an intriguing dissociation into Zn + X at strong compressions was predicted. We find that before the dissociation, a tetragonal P4/nmm phase (4 f.u. cell-1) forms in ZnS and ZnSe driven by the soft phonon mode of the lower-pressure Cmcm phase. A metastable phase with CsCl-like arrangement was proposed for ZnTe as its post-Cmcm structure and was found to match the experimental data concerning both x-ray diffraction patterns and transition pressure. The pressureinduced dissociation for ZnX discovered here has important implications for the behavior of other compounds at high pressure and also for the physics in the Earth's interior. © IOP Publishing Ltd and Deutsche Physikalische Gesellschaft.