Pressure-induced dehydration of dioptase: A single-crystal X-ray diffraction and Raman spectroscopy study

IF 2 4区地球科学 Q3 GEOSCIENCES, MULTIDISCIPLINARY

Comptes Rendus Geoscience Pub Date : 2019-02-01 DOI:10.1016/j.crte.2018.07.007

Fei Qin , Xiang Wu , Shan Qin , Dongzhou Zhang , Vatali B. Prakapenka , Steven D. Jacobsen

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Abstract

We present a synchrotron-based, single-crystal X-ray diffraction and Raman spectroscopy study of natural green dioptase (Cu₆Si₆O₁₈·6H₂O) up to ∼30 GPa at room temperature. The lattice parameters of dioptase exhibit continuous compression behavior up to ∼14.5 GPa, whereupon a structural transition is observed. Pressure–volume data below 14.5 GPa were fitted to a second-order Birch–Murnaghan equation of state with V₀ = 1440(2) Å³ and K₀ = 107(2) GPa, with K₀′ = 4(fixed). The low-pressure form of dioptase exhibits anisotropic compression with axial compressibility β_a > β_c in a ratio of 1.14:1.00. Based on the diffraction data and Raman spectroscopy, the new high-pressure phase could be regarded as a dehydrated form of dioptase in the same symmetry group. Pressure-induced dehydration of dioptase contributes broadly to our understanding of the high-pressure crystal chemistry of hydrous silicates containing molecular water groups.

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压力诱导屈光度脱水的单晶X射线衍射和拉曼光谱研究

我们提出了一个基于同步加速器的单晶x射线衍射和拉曼光谱研究天然绿色透光酶(Cu6Si6O18·6H2O)在室温下高达~ 30 GPa。透辉石的晶格参数表现出连续的压缩行为，高达14.5 GPa，因此观察到结构转变。14.5 GPa以下的压力-体积数据拟合为二阶Birch-Murnaghan状态方程，V0 = 1440(2) Å3, K0 = 107(2) GPa, K0′= 4(固定)。低压形式的透辉石表现为各向异性压缩，轴向压缩率为βa >βc的比例为1.14:1.00。根据衍射数据和拉曼光谱分析，新的高压相可以看作是相同对称基的透辉石的脱水形式。透辉石的压力脱水对我们理解含分子水基的含水硅酸盐的高压晶体化学有很大的帮助。

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来源期刊

Comptes Rendus Geoscience 地学-地球科学综合

CiteScore

2.80

自引率

14.30%

发文量

审稿时长

5.9 weeks

期刊介绍： Created in 1835 by physicist François Arago, then Permanent Secretary, the journal Comptes Rendus de l''Académie des sciences allows researchers to quickly make their work known to the international scientific community. It is divided into seven titles covering the range of scientific research fields: Mathematics, Mechanics, Chemistry, Biology, Geoscience, Physics and Palevol. Each series is led by an editor-in-chief assisted by an editorial committee. Submitted articles are reviewed by two scientists with recognized competence in the field concerned. They can be notes, announcing significant new results, as well as review articles, allowing for a fine-tuning, or even proceedings of symposia and other thematic issues, under the direction of invited editors, French or foreign.