Raman scattering under pressure in ZnGa2Se4

The Raman scattering spectra of ZnGa2Se4 under pressure were investigated at 300 K up to 18.9 GPa. Two stages were observed in the pressure dependences of Raman bands. Such behavior in accordance with the experimental findings existing in literature and was attributed as arising due to the order-disorder phase transition in the cation sublattice. Using the Harrison-Keating's model of the lattice dynamics modified for the crystals with the tetragonal structure, the bulk modulus B and the mode-Gruneisen parameters Gamma(i) were determined for the first time. It is shown that a better agreement between the experimental and calculated values of Gamma(i) is observed, if one takes into consideration different frequency-pressure behavior for the bond-bending and the bond-stretching parameters, which determine the low- (lower than 140 cm(-1)) and high(higher than 140 cm(-1)) frequency phonons, respectively. (C) 2003 Elsevier Ltd. All rights reserved.