| Pressure-induced hydration and order-disorder transition in a synthetic potassium gallosilicate zeolite with gismondine topology. | |
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MedLine Citation:
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PMID: 18266365 Owner: NLM Status: PubMed-not-MEDLINE |
Abstract/OtherAbstract:
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Two high-pressure phases of a potassium gallosilicate with a gismondine framework (K-GaSi-GIS) were characterized using Rietveld refinements of in-situ high-pressure, high-resolution synchrotron X-ray powder diffraction data. The observed response of the K-GaSi-GIS framework under hydrostatic pressure is a gradual flattening of the so-called "double crankshaft" structural chain units. At pressures below 1.0(1) GPa, additional water molecules from the hydrostatic pressure-transmitting medium are inserted into the potassium-water guest network ("pressure-induced hydration") resulting in a "super-hydrated" high-pressure phase I. As the flattening of the double crankshaft structural units in the GIS framework continues above 1.6 GPa, the ellipticity of the cross-linking 8-ring windows is reduced below a certain threshold, and a disordering of the potassium-water guest structure along the 8-ring channel, characteristic of a disordered high-pressure phase II, is observed. The concerted framework distortion and guest network disordering accommodates the increased hydration level while maintaining the seven-fold coordination environment of the potassium cations to framework oxygen atoms and water molecules. We have thus established the atomistic details of a guest-host order-disorder transition under pressure-induced hydration conditions in a zeolite with GIS framework and compared it to other zeolites during pressure-induced hydration. We find that the structural changes mediated by the extra-framework cations and their coordination environment under PIH conditions are at the core of these different mechanisms and are driving the changes in the ellipticity of pore openings, order-disorder and disorder-order transitions, and framework distortions. |
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Authors:
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Yongjae Lee; Sun Jin Kim; Chi-Chang Kao; Thomas Vogt |
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Publication Detail:
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Type: Journal Article Date: 2008-02-12 |
Journal Detail:
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Title: Journal of the American Chemical Society Volume: 130 ISSN: 1520-5126 ISO Abbreviation: J. Am. Chem. Soc. Publication Date: 2008 Mar |
Date Detail:
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Created Date: 2008-02-27 Completed Date: 2008-04-15 Revised Date: - |
Medline Journal Info:
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Nlm Unique ID: 7503056 Medline TA: J Am Chem Soc Country: United States |
Other Details:
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Languages: eng Pagination: 2842-50 Citation Subset: - |
Affiliation:
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Department of Earth System Sciences, Yonsei University, Seoul 120-749, Korea. yongjaelee@yonsei.ac.kr |
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From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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