High pressure elastic properties of simple molecular solids studied by Brillouin scattering
Shimizu Hiroyasu; Kume Tetsuji; Sasaki Shigeo
Abstract:High pressure Brillouin scattering studies are described by presenting a total system for determinations of direction dependent acoustic velocities, refractive index, adiabatic elastic constants, adiabatic bulk modulus, and elastic anisotropy in a simple molecular solid grown in a diamond anvil cell. The detailed method is presented for an orientationally disordered phase III (1.0 less than equivalent to P less than equivalent to .5GPa) of a molecular solid NH3 at 300K. This phase III shows either the molecular rotation or the hydrogen bond. Typical values of three elastic constants are C11 = 21.1, C12 = 17.1, and C44 = 8.1GPa at P = 2.56GPa. The elastic anisotropy, A = 4.05 at 2.56GPa, is almost constant against pressure for fcc crystalline NH sub . These properties are compared with those of solids CH4, Kr, H2S, HCl, and CO2, by concerning with the effects of the molecular rotation and the hydrogen bond under compression. Key Words:brillouin scattering, elastic property, molecular solid, high pressure, elastic constant, acoustic velocity