Raman scattering in CdGa2S4 under pressure

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 a t 14.11 Ga. Using the Harrison-Keating model of the lattice dynamics modifi ed For crystals with the tetragonal structure, the bulk modulus B and the m ode-Gruneisen parameters Gamma (i) were determined fur the first time. A be tter agreement between the experimental and calculated values of Gamma (i) is observed, if one takes into consideration the different behaviour with p ressure for the bond-bonding and the bond-stretching parameters, which dete rmine the low- (lower than 200 cm(-1)) and high- (higher than 200 cm(-1)) f requency phonons, respectively.