High-Pressure Brillouin Studies and Elastic Properties of Single-Crystal H2S Grown in a Diamond Cell

High-pressure Brillouin spectra of crystalline hydrogen sulfide (H(2)S) have been measured at up to 7 gigapascals at room temperature. The best fit of the angular dependence of Brillouin acoustic velocities between experimental values and calculations based on Every's expression for elastic waves of an arbitrary direction yielded the orientation of an H(2)S cubic crystal grown in the diamond-anvil high-pressure cell. In situ determinations of sound velocities, as a function of pressure, could be made for any direction, the refractive index, the density, and the elastic constants. This method provides a means for the systematic study of elastic properties and phase transitions of condensed gases under ultrahigh pressures.