Structure of IIIa-ZnIn2S4 under high pressure

The only member of the II-III2-VI4 semiconductor family with layered struct ure is ZnIn2S4. At ambient conditions several polytypes of this compound ha ve been reported. Energy dispersive X-ray diffraction of ZnIn2S4 has been r ealized at high pressure up to 18 GPa. The structure of this polytype IIIa- ZnIn2S4 is rhombohedral with space group R (3) over bar m. It consists of a close-packed arrangement of S atoms, with Zn and half of the In atoms rand omly distributed on tetrahedral sites, and the other half of the In atoms l ocated on octahedral sites. The hexagonal axes are a = (3.873 +/- 0.002) An gstrom and c = (37.067 +/- 0.004) Angstrom (V = 482 Angstrom(3), Z = 3). NO phase transition has been observed between 0 and 18 GPa. The bulk modulus, obtained by fitting the data to a first-order Murnaghan equation of state is B = (82 +/- 8) GPa.