Single-crystal X-ray diffraction and IR-spectroscopy studies of potassium-deficient fluorapophyllite-(K)

IF 1.2 4区地球科学 Q4 MATERIALS SCIENCE, MULTIDISCIPLINARY Physics and Chemistry of Minerals Pub Date : 2023-02-05 DOI:10.1007/s00269-022-01229-y

Yurii V. Seryotkin, Igor N. Kupriyanov, Mark A. Ignatov

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引用次数: 2

Abstract

Three samples of fluorapophyllite-(K) with different cation composition were studied by the X-ray diffraction and IR-spectroscopy methods. The samples (K_0.72(NH₄)_0.20)_Σ0.92Na_0.08 Ca₄[Al_0.04Si_7.96O₂₀]F·8H₂O from Nidym and K_0.87Na_0.06 Ca₄[Si₈O₂₀]F·8H₂O from Akhaltsykhe localities are characterized by the deficiency of large cations K⁺ and (NH₄)⁺ in the A site; the chemical composition of Talnakh sample (K_0.94(NH₄)_0.06)_Σ1.00 Ca₄[Si₈O₂₀]F·8H₂O is close to the stoichiometric one. The large cations deficiency in the structure of Nidym and Akhaltsykhe samples is compensated by the presence of medium-sized Na⁺ cations, located 1.12–1.31 Å away from the A position. The planar coordination of Na is formed by four H₂O molecules. The occurrence of ammonium ions is found for the Nidym and Talnakh samples and their concentrations are estimated from the IR spectra and structure refinement. Polarized infrared measurements performed for fluorapophyllite-(K) samples oriented along the c-axis reveal pleochroic behavior of the OH absorption bands. The observed pleochroism is explained in terms of absorption from two OH vectors of the H₂O molecules in the crystal structure.

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缺钾氟磷灰石-(K)的单晶x射线衍射和红外光谱研究

用x射线衍射和红外光谱方法研究了3种不同阳离子组成的氟磷灰石样品。Nidym地区的样品(K0.72(NH4)0.20)Σ0.92Na0.08 Ca4[Al0.04Si7.96O20]F·8H2O和Akhaltsykhe地区的样品(K0.87Na0.06 Ca4[Si8O20]F·8H2O)在A位缺乏大阳离子K+和(NH4)+;Talnakh样品(K0.94(NH4)0.06)Σ1.00 Ca4[Si8O20]F·8H2O的化学组成与化学计量值接近。Nidym和Akhaltsykhe样品结构中的大阳离子缺失被位于距离A位置1.12-1.31 Å的中等Na+阳离子的存在所补偿。Na的平面配位是由4个H2O分子形成的。在Nidym和Talnakh样品中发现了铵离子的存在，并根据红外光谱和结构精化估计了它们的浓度。对沿c轴取向的氟磷虾-(K)样品进行的偏振红外测量揭示了OH吸收带的多色性。观察到的多色性是用晶体结构中H2O分子的两个OH载体的吸收来解释的。

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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)