Elastic properties of GaS under high pressure by Brillouin scattering

Abstract

Brillouin scattering from LA phonons in the layered semiconductor GaS has been measured in a diamond anvil cell up to 17.5 GPa. In the same range, linear compressibilities parallel and perpendicular to the c axis have been determined, as well as the ordinary and extraordinary refractive indices. From these data the variations of the elastic constants Cll and C33 and the sound velocities under pressure are deduced. Brillouin data at ambient pressure give the five independent elastic constants of GaS (D6q), and the compressibilities computed from this set of C;J are found to coincide with the values observed in the high-pressure measurements.The optical-index anisotropy decreases to negligible values above 14 GPa. Comparison with an anisotropic modification of Murnaghan's equation of state shows that under high pressure, interand intra-layer forces still retain their individual behavior, although the former have become comparable in magnitude with the latter. Brillouin scattering in the ethanol-methanol mixture has been measured up to 17.5 GPa and the variation of the elastic constant of the fluid is compared with Tait's and Murnaghan's equations of state.

Optical phonon modes in rhombohedral boron monosulfide under high pressure

“…Thus, one can conclude that no phase transition nor amorphization is observed in the studied pressure range. In contrast, one should note that GaS and GaSe do have phase transitions at 18÷19 GPa [28] and 24÷25 GPa [8], respectively. Phase transition of β-GaS observed in [30] was followed by total disappearing of all Raman bands except one.…”

“…That gives rise to "rigid layer modes" (similar to the external modes in molecular crystals) and "Davydov multiplets". However, the Raman studies on the GaSe polytypes [25][26][27][28][29][30] have proved that the layer modes are not dependent on the number of layers.…”

Temperature dependence of the first-order Raman scattering in GaS layered crystals

“…The lattice vibrations of the GaS crystal have been studied by many authors using Raman scattering [1±3], infrared re¯ectivity and absorption [3,4], inelastic neutron scattering [5], and Brillouin scattering measurements [6]. The room temperature Raman scattering spectra of a GaS crystal are measured under pressure up to 20 GPa using a diamond anvil cell, and the pressure coef®cients for all the Ramanactive modes are obtained [7].…”

Hydrostaticity of poly(methyl methacrylate) loaded in a diamond anvil cell for high-pressure study

“…Data of previous reports were also plotted for comparison[3,14,15]. The three data sets are consistent with one another.…”

“…In addition, we will present the pressure dependence of the longitudinal sound velocity and the refractive index of the methanol-ethanol mixture and compare them with previous reports [3,14,15].…”