北京大学学报自然科学版 ›› 2021, Vol. 57 ›› Issue (6): 1079-1086.DOI: 10.13209/j.0479-8023.2021.115

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黑柱石的高压相变及其压缩性研究

吴沈卉1, 黄圣轩1, 秦霏2, 秦善1,†   

  1. 1. 造山带与地壳演化教育部重点实验室, 北京大学地球与空间科学学院, 北京 100871 2. 中国地质大学(北京)地球科学与资源学院, 北京 100083
  • 收稿日期:2020-12-28 修回日期:2021-06-17 出版日期:2021-11-20 发布日期:2021-11-20
  • 通讯作者: 秦善, E-mail: sqin(at)pku.edu.cn
  • 基金资助:
    国家自然科学基金(41772034, 42072047)资助

Phase Transitions and Compressibility of Ilvaite at High Pressures

WU Shenhui1, HUANG Shengxuan1, QIN Fei2, QIN Shan1,†   

  1. 1. Key Laboratory of Orogenic Belts and Crustal Evolution (MOE), School of Earth and Space Sciences, Peking University, Beijing 100871

    2. School of Earth Sciences and Resources, China University of Geosciences (Beijing), Beijing 100083

  • Received:2020-12-28 Revised:2021-06-17 Online:2021-11-20 Published:2021-11-20
  • Contact: QIN Shan, E-mail: sqin(at)pku.edu.cn

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摘要：

利用金刚石压腔(DAC)和原位同步辐射X射线衍射(XRD)技术, 研究天然黑柱石单晶室温下的高压结构稳定性和压缩性, 实验最高压力为39.5 GPa。实验中观察到黑柱石在19.2 GPa 时从斜方晶系α相(空间群Pnam)转变为单斜晶系β相(空间群P21/a), 转变过程中晶胞体积没有明显的不连续变化。利用Birch-Murnaghan状态方程, 对黑柱石单胞体积随压力的变化关系(P-V)进行拟合, 得到α相黑柱石状态方程参数为K0=118(4) GPa, V0=671.9(5) A3, K0′=6.6(7); β相黑柱石初始相变压力Pr=19.2 GPa, 状态方程参数为Kr=157(3) GPa, Vr=599.3(6) A3, Kr′=4 (固定)。此外, 确定了α相和β相黑柱石的轴压缩系数, 并从化学组成和晶体结构压缩性各向异性的角度讨论相变机理。

关键词: 黑柱石, 结构相变, 同步辐射, X射线衍射(XRD)

Abstract:

The high-pressure phase stability and compressibility of a natural orthorhombic symmetry ilvaite are investigated up to 39.5 GPa at room temperature using diamond anvil cell (DAC) combined with in-situ synchrotron radiation single-crystal X-ray diffraction. Experimental results show that ilvaite undergoes a structural transition from an orthorhombic α-phase (Pnam) to a monoclinic β-phase (P21/a) at 19.2 GPa. This structural transformation from α to β phase is displaced without any obvious discontinuity in volume across the transition. The pressure-volume data of ilvaite are described by the third-order Birch-Murnaghan equation of state, yielding K0=118(4) GPa, V0=671.9(5) A3, K0′=6.6(7) for α-ilvaite and Kr=157(3) GPa, Vr=599.3(6) A3, K0′=4(fixed) with a phase transition pressure Pr=19.2 GPa for β-ilvaite. In addition, the axial compression coefficients for both α- and β-ilvaites are determined, and the mechanism of the pressure-induced Pnam to P21/a phase transition is discussed in the views of crystal structure and the anisotropy of compressibility.

Key words: ilvaite, structural transitions, synchrotron radiation, X-ray diffraction (XRD)

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