Elastic properties and sound velocities of superionic ice X and ice XVIII are investigated using ab initio molecular dynamics at 200 GPa and temperatures up to 4500 K. The dislocation of protons from their lattice sites leads to the significant elastic softening in ice X with increasing temperature. The phase transition from ice X to ice XVIII leads to an increasing in proton diffusion and elastic softening at 2000 K. We also observed the elastic stiffening with increasing temperature from 2000 to 3000 K in ice XVIII, which is similar to the behavior of some liquids. Above 3000 K, all the elastic constants decrease dramatically. Our study suggests proton diffusion has significant influence on the elastic properties, and the elastic property of superionic ice with increasing temperature is different from ordinary solids.

中文翻译：

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超离子冰的异常弹性

从头开始研究超离子冰X和冰XVIII的弹性和声速在200 GPa和最高4500 K的温度下具有分子动力学。质子从晶格位置的错位导致温度X随冰X的显着弹性软化。从冰X到冰XVIII的相变导致2000 K时质子扩散增加和弹性软化。我们还观察到在冰XVIII中温度从2000 K增加到3000 K时，弹性刚度随温度的升高而变化。这类似于某些液体的行为。高于3000 K时，所有弹性常数都会急剧降低。我们的研究表明质子扩散对弹性性能有重要影响，并且随着温度升高，超离子冰的弹性与普通固体不同。