Raman Scattering in CdGa2S4 under Pressure

Abstract

The Raman active modes of CdGa2S4 were investigated at 300 K under pressure up to 14.11 GPa. Two stages in the pressure dependence of Raman bands were attributed to the order–disorder phase transition in the cation sublattice. A pressure induced reversible first-order phase transition was observed at 14.11 GPa. Using the Harrison-Keating model of the lattice dynamics modified for crystals with the tetragonal structure, the bulk modulus B and the mode-Grüneisen parameters Γi were determined for the first time. A better agreement between the experimental and calculated values of Γi is observed, if one takes into consideration the different behaviour with pressure for the bond-bending and the bond-stretching parameters, which determine the low- (lower than 200 cm—1) and high- (higher than 200 cm—1) frequency phonons, respectively.