G. Zeff, B. Kalkan, K. Armstrong, M. Kunz, Q. Williams
{"title":"High pressure raman spectroscopy and X-ray diffraction of K2Ca(CO3)2 bütschliite: multiple pressure-induced phase transitions in a double carbonate","authors":"G. Zeff, B. Kalkan, K. Armstrong, M. Kunz, Q. Williams","doi":"10.1007/s00269-023-01262-5","DOIUrl":null,"url":null,"abstract":"<div><p>The crystal structure and bonding environment of K<sub>2</sub>Ca(CO<sub>3</sub>)<sub>2</sub> bütschliite were probed under isothermal compression via Raman spectroscopy to 95 GPa and single crystal and powder X-ray diffraction to 12 and 68 GPa, respectively. A second order Birch-Murnaghan equation of state fit to the X-ray data yields a bulk modulus, <span>\\({K}_{0}=46.9\\)</span> GPa with an imposed value of <span>\\({K}_{0}^{\\prime}= 4\\)</span> for the ambient pressure phase. Compression of bütschliite is highly anisotropic, with contraction along the <i>c</i>-axis accounting for most of the volume change. Bütschliite undergoes a phase transition to a monoclinic <i>C</i>2/<i>m</i> structure at around 6 GPa, mirroring polymorphism within isostructural borates. A fit to the compression data of the monoclinic phase yields <span>\\({V}_{0}=322.2\\)</span> Å<sup>3</sup><span>\\(,\\)</span> <span>\\({K}_{0}=24.8\\)</span> GPa and <span>\\({K}_{0}^{\\prime}=4.0\\)</span> using a third order fit; the ability to access different compression mechanisms gives rise to a more compressible material than the low-pressure phase. In particular, compression of the <i>C</i>2/<i>m</i> phase involves interlayer displacement and twisting of the [CO<sub>3</sub>] units, and an increase in coordination number of the K<sup>+</sup> ion. Three more phase transitions, at ~ 28, 34, and 37 GPa occur based on the Raman spectra and powder diffraction data: these give rise to new [CO<sub>3</sub>] bonding environments within the structure.</p></div>","PeriodicalId":20132,"journal":{"name":"Physics and Chemistry of Minerals","volume":null,"pages":null},"PeriodicalIF":1.2000,"publicationDate":"2024-01-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00269-023-01262-5.pdf","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Physics and Chemistry of Minerals","FirstCategoryId":"89","ListUrlMain":"https://link.springer.com/article/10.1007/s00269-023-01262-5","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 crystal structure and bonding environment of K2Ca(CO3)2 bütschliite were probed under isothermal compression via Raman spectroscopy to 95 GPa and single crystal and powder X-ray diffraction to 12 and 68 GPa, respectively. A second order Birch-Murnaghan equation of state fit to the X-ray data yields a bulk modulus, \({K}_{0}=46.9\) GPa with an imposed value of \({K}_{0}^{\prime}= 4\) for the ambient pressure phase. Compression of bütschliite is highly anisotropic, with contraction along the c-axis accounting for most of the volume change. Bütschliite undergoes a phase transition to a monoclinic C2/m structure at around 6 GPa, mirroring polymorphism within isostructural borates. A fit to the compression data of the monoclinic phase yields \({V}_{0}=322.2\) Å3\(,\)\({K}_{0}=24.8\) GPa and \({K}_{0}^{\prime}=4.0\) using a third order fit; the ability to access different compression mechanisms gives rise to a more compressible material than the low-pressure phase. In particular, compression of the C2/m phase involves interlayer displacement and twisting of the [CO3] units, and an increase in coordination number of the K+ ion. Three more phase transitions, at ~ 28, 34, and 37 GPa occur based on the Raman spectra and powder diffraction data: these give rise to new [CO3] bonding environments within the structure.
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)