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首页> 外文期刊>Earth and Planetary Science Letters: A Letter Journal Devoted to the Development in Time of the Earth and Planetary System >Thermoelastic properties of ice VII and its high-pressure polymorphs: Implications for dynamics of cold slab subduction in the lower mantle
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Thermoelastic properties of ice VII and its high-pressure polymorphs: Implications for dynamics of cold slab subduction in the lower mantle

机译：VII冰及其高压多晶型的热弹性性质：对下地幔冷板俯冲动力学的影响

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Acoustic velocities in polycrystalline H_2O ice have been measured at room temperature in a pressure range 6-60GPa by a Brillouin scattering method. Synchrotron X-ray diffraction measurements were also conducted simultaneously with the Brillouin scattering measurements in a pressure range 40-60GPa. The obtained elastic moduli of high-pressure ice indicate that bcc-structured ice undergoes two transitions related to a change in the hydrogen bonding state at approximately 40GPa and 58GPa, i.e. transitions of ice VII to the pre-transitional state of ice VII at 40GPa and to the dynamically disordered ice X at 58GPa, respectively. This observation is consistent with previous spectroscopic studies and X-ray diffraction studies. Pressure dependencies of adiabatic elastic moduli and specific heat for ice VII and its high-pressure polymorphs were obtained from the acoustic velocity and volume data measured in this study. Isothermal compression data were obtained from previous studies. The relationships between pressure and adiabatic elastic moduli for ice VII were obtained as follows: K_s=4.0(2)+8.51(4)×P-0.081(2)×P~2+5.2(4)×10~(-4)×P~3; μ_s=14(2)+1.7(3)×P-0.04(2)×P~2+5(3)×10~(-4)×P~3. An empirical relationship between specific heat and pressure at room temperature was obtained for ice VII as follows: C_p=3.3(2)+22.1(1)×e~(-0.058(2)P). This result implies that the transition from ice VII to the dynamically disordered ice X is accompanied with a discontinuous change in several thermodynamic properties of ice. The elasticity difference between ice VII and the dynamically disordered ice X may affect the dynamics of cold subducting slabs in Earth's lower mantle and the interiors of icy planets. The thermoelastic properties of high-pressure polymorphs of ice obtained in this study could contribute to clarifying the dynamics and the evolution of Earth and icy planets and satellites.
机译：通过布里渊散射法在室温下在6-60GPa的压力下测量了多晶H_2O冰中的声速。同步辐射X射线衍射测量与布里渊散射测量同时在40-60GPa的压力范围内进行。所获得的高压冰的弹性模量表明，密实结构的冰经历了两个与氢键态在大约40GPa和58GPa时的氢键态变化有关的转变，即，VII在40GPa和70GPa时转变为冰VII的过渡前态。分别达到58GPa的动态无序冰X。该观察结果与先前的光谱学研究和X射线衍射研究一致。从这项研究中测得的声速和体积数据获得了冰VII及其高压多晶型的绝热弹性模量和比热的压力依赖性。等温压缩数据是从以前的研究中获得的。冰VII的压力与绝热弹性模量之间的关系如下：K_s = 4.0（2）+8.51（4）×P-0.081（2）×P〜2 + 5.2（4）×10〜（-4） ×P〜3; μ_s= 14（2）+1.7（3）×P-0.04（2）×P〜2 + 5（3）×10〜（-4）×P〜3。对于冰VII，获得了在室温下比热和压力之间的经验关系，如下：C_p = 3.3（2）+22.1（1）×e〜（-0.058（2）P）。该结果暗示从冰VII到动态无序的冰X的转变伴随着冰的几种热力学性质的不连续变化。冰VII和动态无序的冰X之间的弹性差异可能会影响地球下地幔和冰行星内部的冷俯冲板的动力学。这项研究中获得的高压冰晶型的热弹性性质可能有助于阐明地球以及冰冷的行星和卫星的动力学和演化。

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