<br>高达 1 Mbar 的 MgCl2 的高压 X 射线衍射、拉曼和计算研究：β-MgCl2 层状结构的广泛压力稳定性。,Scientific Reports

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高达 1 Mbar 的 MgCl2 的高压 X 射线衍射、拉曼和计算研究：β-MgCl2 层状结构的广泛压力稳定性。
Scientific Reports ( IF 3.8 ) Pub Date : 2016-08-12 , DOI: 10.1038/srep30631
Elissaios Stavrou ₁ , Yansun Yao _{2,

3} , Joseph M Zaug ₁ , Sorin Bastea ₁ , Bora Kalkan _{4,

5} , Zuzana Konôpková ₆ , Martin Kunz ₄

Affiliation

使用同步加速器角色散粉末 X 射线衍射和拉曼光谱，使用室温下高达 100 GPa 的金刚石砧池，对具有菱形层状 CdCl2 型结构 (α-MgCl2) 的氯化镁 (MgCl2) 进行了实验研究，并进行了理论研究使用第一原理密度泛函计算。结果表明，在 0.7 GPa 压力下，压力诱导的二级结构相变为六方层状 CdI2 型结构 (β-MgCl2)：Cl 阴离子的堆积顺序发生改变，导致 c 轴长度缩短。理论计算证实了这种相变顺序，并且计算出的转变压力与实验非常吻合。晶格动力学计算还重现了环境压力和高压阶段测量的实验拉曼光谱。根据我们的实验结果，MgCl2 在高达 100 GPa 的压力下仍保持二维层状相，并且进一步保留了 Mg 阳离子的 6 倍配位。相对热函的理论计算表明，这种广泛的压力稳定性是由于层状结构的低热函排除了动力学势垒效应。这一观察结果很不寻常，因为它与高度压缩的 AB2 化合物的一般结构行为相矛盾。

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High-pressure X-ray diffraction, Raman, and computational studies of MgCl2 up to 1 Mbar: Extensive pressure stability of the β-MgCl2 layered structure.

Magnesium chloride (MgCl2) with the rhombohedral layered CdCl2-type structure (α-MgCl2) has been studied experimentally using synchrotron angle-dispersive powder x-ray diffraction and Raman spectroscopy using a diamond-anvil cell up to 100 GPa at room temperature and theoretically using first-principles density functional calculations. The results reveal a pressure-induced second-order structural phase transition to a hexagonal layered CdI2-type structure (β-MgCl2) at 0.7 GPa: the stacking sequence of the Cl anions are altered resulting in a reduction of the c-axis length. Theoretical calculations confirm this phase transition sequence and the calculated transition pressure is in excellent agreement with the experiment. Lattice dynamics calculations also reproduce the experimental Raman spectra measured for the ambient and high-pressure phase. According to our experimental results MgCl2 remains in a 2D layered phase up to 100 GPa and further, the 6-fold coordination of Mg cations is retained. Theoretical calculations of relative enthalpy suggest that this extensive pressure stability is due to a low enthalpy of the layered structure ruling out kinetic barrier effects. This observation is unusual, as it contradicts with the general structural behavior of highly compressed AB2 compounds.

更新日期：2017-01-31

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