Structural disorder in Fe-bearing topaz-OH revealed by single-crystal X-ray diffraction

IF 1.5 4区地球科学 Q4 MATERIALS SCIENCE, MULTIDISCIPLINARY

Physics and Chemistry of Minerals Pub Date : 2026-03-13 DOI:10.1007/s00269-026-01342-2

Baoyun Wang, Meisu Xiang

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Abstract

Topaz-OH phases, including structurally distinct but chemically identical topaz-OH I and topaz-OH II, are considered as potential water carriers in hydrated subducted sediments. In this study, Fe-bearing topaz-OH I was synthesized at 15.5 GPa and 1400 °C, with a chemical composition of Al_1.94±0.05Fe_0.18±0.01Si_0.69±0.02O₆H_2.88±0.13. Its crystal structure is similar to that of the ordered Al-endmember topaz-OH I (Al₂SiO₆H₂), with both exhibiting the same Pbnm space group and comparable unit cell parameters. However, this structure contains evident vacancies in the tetrahedral sites and new occupied octahedral sites that are normally vacant in the ordered Al-endmember topaz-OH I. Our structural model represents a transitional phase between the Al/Si-ordered topaz-OH I and the fully Al/Si-disordered topaz-OH II. These findings suggest that structural disorder may play a key role in influencing the tetrahedral-to-octahedral occupancy ratio, the evolution of crystal structures, and the thermal stability of topaz-OH under the high pressure-temperature conditions of the deep mantle.

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单晶x射线衍射揭示含铁黄玉- oh的结构紊乱

托帕石- oh相，包括结构不同但化学性质相同的托帕石- oh - I和托帕石- oh - II，被认为是水合俯冲沉积物中潜在的水载体。本研究在15.5 GPa和1400℃条件下合成了含铁的topazoh I，化学成分为Al1.94±0.05Fe0.18±0.01Si0.69±0.02O6H2.88±0.13。其晶体结构与有序al端元topazoh - I （Al2SiO6H2）相似，具有相同的Pbnm空间基团和相似的单晶参数。然而，这种结构包含明显的四面体空位和新占用的八面体空位，这些空位通常在有序的Al端元topazoh - I中是空的。我们的结构模型代表了Al/ si有序topazoh - I和完全Al/ si无序topazoh - II之间的过渡阶段。这些结果表明，在深部地幔高压-高温条件下，结构紊乱可能是影响托帕石- oh的四面体-八面体占位率、晶体结构演化和热稳定性的关键因素。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

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来源期刊

Physics and Chemistry of Minerals 地学-材料科学：综合

CiteScore

2.90

自引率

14.30%

发文量

审稿时长

3 months

期刊介绍： Physics and Chemistry of Minerals is an international journal devoted to publishing articles and short communications of physical or chemical studies on minerals or solids related to minerals. The aim of the journal is to support competent interdisciplinary work in mineralogy and physics or chemistry. Particular emphasis is placed on applications of modern techniques or new theories and models to interpret atomic structures and physical or chemical properties of minerals. Some subjects of interest are: -Relationships between atomic structure and crystalline state (structures of various states, crystal energies, crystal growth, thermodynamic studies, phase transformations, solid solution, exsolution phenomena, etc.) -General solid state spectroscopy (ultraviolet, visible, infrared, Raman, ESCA, luminescence, X-ray, electron paramagnetic resonance, nuclear magnetic resonance, gamma ray resonance, etc.) -Experimental and theoretical analysis of chemical bonding in minerals (application of crystal field, molecular orbital, band theories, etc.) -Physical properties (magnetic, mechanical, electric, optical, thermodynamic, etc.) -Relations between thermal expansion, compressibility, elastic constants, and fundamental properties of atomic structure, particularly as applied to geophysical problems -Electron microscopy in support of physical and chemical studies -Computational methods in the study of the structure and properties of minerals -Mineral surfaces (experimental methods, structure and properties)