{"title":"高压下羟基叶绿石(K)的结构演变","authors":"Yurii V. Seryotkin","doi":"10.1007/s00269-023-01265-2","DOIUrl":null,"url":null,"abstract":"<div><p>The high-pressure structural evolution of a natural hydroxyapophyllite-(K) K<sub>0.96</sub> Ca<sub>4.01</sub>[Al<sub>0.01</sub>Si<sub>7.99</sub>O<sub>20</sub>]((OH)<sub>0.95</sub>F<sub>0.05</sub>)·(H<sub>2</sub>O)<sub>8.14</sub>, <i>Z</i> = 2, <i>a</i> = 8.9699(1), <i>c</i> = 15.8934(3) Å, space group <i>P</i>4/<i>mnc</i>, from the Hatrurim Basin, Negev Desert, compressed in penetrating (ethanol:water 8:1 mixture) medium up to 5 GPa, was studied by single-crystal X-ray diffraction with a diamond anvil cell. The results clearly demonstrate the absence of pressure-induced hydration in the structure. Within 3 GPa, the compression mechanism is similar to that known in fluorapophyllite-(K). The compression in the plane of silicate layer proceeds via the relative rotation of the four-membered rings. The compression along the <i>c-</i>axis proceeds through the shortening of the inter-layer distance, whereas the thickness of silicate layer remains almost unchanged. As a result, the pressure-induced changes in the unit-cell metrics are similar to those for fluorapophyllite-(K). At about 3 GPa, hydroxyapophyllite-(K) undergoes a phase transition with the symmetry lowering to orthorhombic (space group <i>Pnnm</i>). The symmetry of the high-pressure phase allows deformation of the four-membered rings of the silicate layer, which is impossible within tetragonal symmetry. In this case, the structure is compressed much more along the <i>a</i>-axis than along the <i>b</i>-axis. As a result, the orthorhombic phase of hydroxyapophyllite-(K) is more compressible compared to fluorapophyllite-(K).</p></div>","PeriodicalId":20132,"journal":{"name":"Physics and Chemistry of Minerals","volume":"51 1","pages":""},"PeriodicalIF":1.2000,"publicationDate":"2024-01-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":"{\"title\":\"Structure evolution of hydroxyapophyllite-(K) under high pressure\",\"authors\":\"Yurii V. 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The compression along the <i>c-</i>axis proceeds through the shortening of the inter-layer distance, whereas the thickness of silicate layer remains almost unchanged. As a result, the pressure-induced changes in the unit-cell metrics are similar to those for fluorapophyllite-(K). At about 3 GPa, hydroxyapophyllite-(K) undergoes a phase transition with the symmetry lowering to orthorhombic (space group <i>Pnnm</i>). The symmetry of the high-pressure phase allows deformation of the four-membered rings of the silicate layer, which is impossible within tetragonal symmetry. In this case, the structure is compressed much more along the <i>a</i>-axis than along the <i>b</i>-axis. 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引用次数: 0
摘要
天然羟基叶绿石-(K) K0.96 Ca4.01[Al0.01Si7.99O20]((OH)0.95F0.05)-(H2O)8.14, Z = 2, a = 8.9699(1), c = 15.通过使用金刚石砧室进行单晶 X 射线衍射,研究了来自内盖夫沙漠 Hatrurim 盆地、在渗透介质(乙醇:水 8:1 混合物)中被压缩至 5 GPa、空间群为 P4/mnc 的 OO20]((OH)0.95F0.05-(H2O)8.14)。研究结果清楚地表明,该结构中不存在压力引起的水合作用。在 3 GPa 的范围内,压缩机制与已知的氟叶绿石-(K)类似。硅酸盐层平面内的压缩是通过四元环的相对旋转进行的。沿 c 轴的压缩是通过缩短层间距离进行的,而硅酸盐层的厚度几乎保持不变。因此,压力引起的单位晶胞度量变化与氟叶绿石(K)相似。在大约 3 GPa 的压力下,羟基叶蜡石(K)发生相变,对称性降低为正方晶(空间群 Pnnm)。高压相的对称性允许硅酸盐层的四元环发生变形,而这在四方对称性中是不可能发生的。在这种情况下,结构沿 a 轴的压缩程度远远大于沿 b 轴的压缩程度。因此,羟基叶绿石-(K)的正方相比氟叶绿石-(K)更容易压缩。
Structure evolution of hydroxyapophyllite-(K) under high pressure
The high-pressure structural evolution of a natural hydroxyapophyllite-(K) K0.96 Ca4.01[Al0.01Si7.99O20]((OH)0.95F0.05)·(H2O)8.14, Z = 2, a = 8.9699(1), c = 15.8934(3) Å, space group P4/mnc, from the Hatrurim Basin, Negev Desert, compressed in penetrating (ethanol:water 8:1 mixture) medium up to 5 GPa, was studied by single-crystal X-ray diffraction with a diamond anvil cell. The results clearly demonstrate the absence of pressure-induced hydration in the structure. Within 3 GPa, the compression mechanism is similar to that known in fluorapophyllite-(K). The compression in the plane of silicate layer proceeds via the relative rotation of the four-membered rings. The compression along the c-axis proceeds through the shortening of the inter-layer distance, whereas the thickness of silicate layer remains almost unchanged. As a result, the pressure-induced changes in the unit-cell metrics are similar to those for fluorapophyllite-(K). At about 3 GPa, hydroxyapophyllite-(K) undergoes a phase transition with the symmetry lowering to orthorhombic (space group Pnnm). The symmetry of the high-pressure phase allows deformation of the four-membered rings of the silicate layer, which is impossible within tetragonal symmetry. In this case, the structure is compressed much more along the a-axis than along the b-axis. As a result, the orthorhombic phase of hydroxyapophyllite-(K) is more compressible compared to fluorapophyllite-(K).
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)