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

我们测定了水和D2O冰在300K和压力在1.05~2.1 GPa时的任意方向的声速、折射率、绝热弹性常数和绝热体积模数。对于立方冰VI，当压力在1.05~2.1 GPa时，直到8 GPa时，水冰VI的弹性常数的典型值是C_&lt；11&gt；=32.8，C_&lt；12&gt；=11.8，C_&lt；13&gt；=14.7，C_&lt；33&gt；=27.8，C&lt；44&gt；=6.3，当压力为1.23 Gpa时，C_&lt；66&gt；=5.9 Gpa。此外，对于H_2O冰VII，在P=4.7 Gpa时，3个弹性常数的取值分别为C_&lt；11&gt；=57，C_&lt；12&gt；=31和C_&lt；44&gt；=32。在观测的压力范围内，H_2O和D_2O的折射率和弹性常数没有差别。在2.1 GPaVI*VII相变时，声速、折射率和弹性常数呈现剧烈变化，但绝热体积模数呈现出几乎连续的变化，这最有可能与VI和VII冰中自包络结构的共同特征和势函数有关。这些由布里渊光谱研究的结果在高压世界是值得注意的。

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.