High-pressure elastic properties of VI, VII and VIII phases in dense H_2O ice by Brillouin Scattering

我们测定了H_2O和D_2O冰在300K、压力在1.05 ~ 2.1 GPa之间（四方冰VI）和压力在8gpa以上（立方冰VII）的任何方向上的声速、折射率、绝热弹性常数和绝热体模量。在1.23 GPa压力下，H_2O冰VI弹性常数的典型值为C_<11>=32.8, C_<12>=11.8, C_<13>=14.7, C_<33>=27.8, C_<44>=6.3, C_<66>=5.9 GPa，而H_2O冰VII弹性常数的典型值为C_<11>=57, C_<12>=31, C_<44>=32， P=4.7 GPa。折射率和弹性常数表明，在观测到的压力范围内，H_2O和D_2O没有差别。在2.1 GPa时，VI*VII冰的声速、折射率和弹性常数发生了剧烈变化，但绝热体模量几乎呈连续变化，这很可能与VI和VII冰的自包合物结构和势函数的共同特征有关。用布里渊光谱研究的这些结果在高压环境中是值得注意的。

We have determined acoustic velocities in any direction, refractive index, adiabatic elastic constants, and adiabatic bulk modulus of H_2O and D_2O ices at 300K and at pressures between 1.05 and 2.1 GPa for tetragonal ice VI and above pressures up to 8 GPa for cubic ice VII.Typical values of elastic constants for H_2O ice VI are C_<11>=32.8, C_<12>=11.8, C_<13>=14.7, C_<33>=27.8, C_<44>=6.3, and C_<66>=5.9 GPa at the pressure of 1.23 GPa Moreover, for H_2O ice VII the values of 3 elastic constants are C_<11>=57, C_<12>=31, and C_<44>=32, GPa at P=4.7 GPa. Refractive index and elastic constants show no distinction between H_2O and D_2O over the observed pressure ranges. At ice VI*VII transition at 2.1 GPa, acoustic velocities, refractive index, and elastic constants present drastic change, but the adiabatic bulk modulus shows almost continuous change which is most likely to relate the common features of the selfclathrate structure and the potential function in both VI and VII ices.These results studied by Brillouin Spectroscopy are noticeable in the high-pressure world.