Equations of state of magnesium silicates anhydrous B and superhydrous B
Equations of state of magnesium silicates anhydrous B and superhydrous B
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无水硅酸镁B和过水硅酸镁B的状态方程
DOI：
10.1007/s002690050220
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发表时间：
1999
影响因子：
1.4
通讯作者：
T. Gasparik
中科院分区：
文献类型：
--
作者：
W. Crichton;N. Ross;T. Gasparik
在室温下，对无水B和超水B分别进行了7.3和7.7 GPa的高压单晶X射线衍射实验。用三阶Birch-Murnaghan状态方程拟合Anhy-B和Shy-B的P-V数据，得到Anhy-B的V0 = 838.86 ± 0.04GPa，KT，0 = 151.5 ± 0.9GPa，K′ = 5.5 ± 0.3; Shy-B的V0 = 624.71 ± 0.03GPa，KT，0 = 142.6 ± 0.8GPa，K′ = 5.8 ± 0.2。对Anhy-B轴向压缩的类似分析表明，c轴最可压缩（Kc = 137 ± 3 GPa），b轴最不可压缩（Kb = 175 ± 4 GPa），a轴居中（Ka = 148 ± 1 GPa）。在Shy-B中，a轴的可压缩性最大（Ka = 135 ± 1 GPa），其次是B轴和c轴，它们具有相似的压缩性（KB = 146 ± 3 GPa; Kc = 148 ± 3 GPa）。Shy-B的b轴比Anhy-B的可压缩性高出约16%，这主要是由于H原子所在的O-T层以及与相邻O层的连接的差异。在O层中MgO 6和SiO 6八面体的刚性边缘共享链控制两种结构中沿沿着a-和c-轴的可压缩性。最终结果是整体各向异性压缩从Anhy-B中的1.22%降低到Shy-B中的1.9%。
Abstract High-pressure single crystal X-ray diffraction experiments of phase anhydrous B and superhydrous B have been carried out to 7.3 and 7.7 GPa, respectively, at room temperature. Fitting a third-order Birch-Murnaghan equation of state to the P-V data yields values of V0 = 838.86 ± 0.04 Å3, KT,0 = 151.5 ± 0.9 GPa and K′ = 5.5 ± 0.3 for Anhy-B and V0 = 624.71 ± 0.03 Å3, KT,0 = 142.6 ± 0.8 GPa and K′ = 5.8 ± 0.2 for Shy-B. A similar analysis of the axial compressibilities in Anhy-B reveals that the c-axis is most compressible (Kc = 137 ± 3 GPa), the b-axis is least compressible (Kb = 175 ± 4 GPa), and the a-axis is intermediate (Ka = 148 ± 1 GPa). In Shy-B, the a-axis is most compressible (Ka = 135 ± 1 GPa), followed by the b- and c-axes which have similar compressibilities (Kb = 146 ± 3 GPa; Kc = 148 ± 3 GPa). The fact that the b-axis of Shy-B is approximately 16% more compressible than Anhy-B is primarily due to differences in the O-T layer in which the H atoms are located and the linkages with the adjacent O layers. The rigid edge-sharing chains of MgO6 and SiO6 octahedra in the O layer control compressibility along the a- and c-axes in both structures. The net result is a reduction in the overall anisotropic compression from ∼22% in Anhy-B to ∼9% in Shy-B.