ブリルアン散乱による高圧力下の単純分子固体の弾性的性質の研究

抄録

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≤P≤3.5GPa) 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 NH₃. 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.