{"title":"Structure evolution of hydroxyapophyllite-(K) under high pressure","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":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Physics and Chemistry of Minerals","FirstCategoryId":"89","ListUrlMain":"https://link.springer.com/article/10.1007/s00269-023-01265-2","RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q4","JCRName":"MATERIALS SCIENCE, MULTIDISCIPLINARY","Score":null,"Total":0}
引用次数: 0
Abstract
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)