Atomic-scale deformation mechanisms at high-pressure in hydroboracite, CaMg[B₃O₄(OH)₃]₂·3H₂O

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

Physics and Chemistry of Minerals Pub Date : 2026-02-25 DOI:10.1007/s00269-026-01339-x

Davide Comboni, Paolo Lotti, Lisa Chiappella, Tommaso Battiston, Gaston Garbarino, Paola Giura, G. Diego Gatta

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Abstract

The high-pressure behaviour of hydroboracite [ideally CaMg[B₃O₄(OH)₃]₂·3H₂O, Sp. Gr. P2/c with a ~ 11.769, b ~ 6.684, c ~ 8.235 Å, and β ~ 102.6° at room conditions] has been studied by two in-situ single-crystal synchrotron X-ray diffraction experiments up to about 15 GPa, using He as pressure-transmitting medium. Between 14.51(5) and 14.72(5) GPa, hydroboracite undergoes a first-order phase transition to its high-pressure polymorph, hydroboracite-II (likely monoclinic with a ~ 11.29, b ~ 6.297, c ~ 7.48 Å, and β ~ 106°, space group unknown). The isothermal bulk modulus (K_V0 = β⁻¹_P0,T0, where β_P0,T0 is the volume compressibility coefficient) of hydroboracite was found to be K_V0 = 41.4(6) GPa. The destructive nature of the phase transition prevented any structure resolution of hydroboracite-II or even the continuation of the experiments at pressures higher than 15.45(5) GPa. In the pressure range 0–14.45(5) GPa, the compressional anisotropy of hydroboracite, indicated by the ratio between the principal components of the unit-strain ellipsoid, is ε₁:ε₂:ε₃ = 2.2:1.3:1. The P-induced deformation mechanisms at the atomic scale in hydroboracite are here described.

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水硼砂CaMg[B₃O₄（OH）₃]₂·3H₂O在高压下的原子尺度变形机理

以He为传压介质，通过两次原位单晶同步x射线衍射实验，研究了水硼砂(理想情况下为CaMg[B₃O₄（OH）₃]₂·3H₂O, Sp. Gr. P2/c （a ~ 11.769, B ~ 6.684, c ~ 8.235 Å， β ~ 102.6°）在室温下的高压行为。在14.51(5)~ 14.72(5)GPa之间，水硼砂发生一级相变，形成高压多晶型水硼砂- ii（可能为单斜晶型，a ~ 11.29, b ~ 6.297, c ~ 7.48 Å， β ~ 106°，空间群未知）。等温体积模量（KV0 = β - 1P0,T0，其中β p0，T0为体积压缩系数）为KV0 = 41.4(6) GPa。在高于15.45(5)GPa的压力下，相变的破坏性阻碍了氢硼酸盐- ii的结构分解，甚至阻碍了实验的继续。在0 ~ 14.45(5)GPa压力范围内，由单位应变椭球主成分之比表示的水硼砂的挤压各向异性为ε1:ε2:ε3 = 2.2:1.3:1。本文描述了水硼砂在原子尺度上的p致变形机制。

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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)