Pressure-induced structural changes in ZnS

We report detailed data on the structural parameters and equations of state of high-density ZnS obtained by x-ray diffraction using synchrotron radiat ion for pressures below 96 GPa. It is shown that initial room condition pha ses of ZnS, zinc blende and wurtzite, transform unambiguously to the rocksa lt structure at 12 GPa and at room temperature. Our data hence rule out the existence of an intermediate phase of the cinnabar type in ZnS. The initia l zinc-blende and wurtzite phases present quantitatively similar equations of state parametrized by B-0 = 79.5 GPa and B'(0) = 4, and B-0 = 80.1 GPa a nd B'(0) = 4, respectively. As compared to the initial phases, the rocksalt phase, adopted at higher pressure, is denser and less compressible with B- 0 = 117.6 GPa and B'(0) = 4. The high-pressure rocksalt structure is also s hown to be unstable for pressures in excess of 65 GPa, leading to a transit ion to the Cmcm structure, an orthorhombic distortion, without a significan t change in volume. The occurrence of the Cmcm structure in dense ZnS is in line with the observed dense phases in other zinc chalcogenides.