Stability and structural properties of ZnS and ZnSe under high pressure

The structural phase transformations of ZnS and ZnSe under high pressure ar e studied by using a first-principles pseudopotential method and the local density approximation for the exchange-correlation potential. ZnS and ZnSe: are found to have very similar structural systematics under high pressure. In both compounds, the SC16 phase (simple cubic with 16-atom basis) is pre dicted to be thermodynamically stable before the lock-salt structure. The c innabar structure of both systems is found to be unstable. The structural p roperties of the zinc-blende, rock-salt, cinnabar and SC16 phases are prese nted.