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Time-resolved structural analysis of K- and Ba-exchange reactions with synthetic Na-birnessite using synchrotron X-ray diffraction

Christina L. Lopano, Peter J. Heaney, Jeffrey E. Post, Jonathan Hanson and Sridhar Komarneni
Time-resolved structural analysis of K- and Ba-exchange reactions with synthetic Na-birnessite using synchrotron X-ray diffraction (in Microbeam cathodoluminescence, Ian M. Coulson (prefacer), Paul R. Edwards (prefacer) and Martin R. Lee (prefacer))
American Mineralogist (February 2007) 92 (2-3): 380-387

Abstract

Time-resolved Rietveld refinements using synchrotron X-ray diffraction (XRD) have documented real-time changes in unit-cell parameters in response to cation substitution in synthetic Na-birnessite. Potassium- and Ba-birnessite, like Na-birnessite, were found to have triclinic symmetry. Rietveld analyses of the XRD patterns for K- and Ba-exchanged birnessite revealed decreases in the a, c, and beta unit-cell parameters, with a decrease of 1.7 and 0.5%, respectively, in unit-cell volume relative to Na-birnessite. Fourier electron difference syntheses revealed that the changes in the configuration of the interlayer species, and the charge, size, and hydration of the substituting cations, serve as the primary controls on changes in unit-cell parameters. Split electron density maxima with centers at (0 0 0.5) were present for Na, K, and Ba end-members; however, with increased substitution of K (super +) for Na (super +) , the axis connecting the split-site maxima rotated from an orientation parallel to the b-axis to along the a-axis. Substitution of Ba (super 2+) for Na (super +) did not result in rotation, but splitting of the interlayer site was more pronounced.


ISSN: 0003-004X
EISSN: 1945-3027
Coden: AMMIAY
Serial Title: American Mineralogist
Serial Volume: 92
Serial Issue: 2-3
Title: Time-resolved structural analysis of K- and Ba-exchange reactions with synthetic Na-birnessite using synchrotron X-ray diffraction
Title: Microbeam cathodoluminescence
Author(s): Lopano, Christina L.Heaney, Peter J.Post, Jeffrey E.Hanson, JonathanKomarneni, Sridhar
Author(s): Coulson, Ian M.prefacer
Author(s): Edwards, Paul R.prefacer
Author(s): Lee, Martin R.prefacer
Affiliation: Penn State University, Department of Geosciences, University Park, PA, United States
Affiliation: University of Regina, Department of Geology, Regina, SK, Canada
Pages: 380-387
Published: 200702
Text Language: English
Publisher: Mineralogical Society of America, Washington, DC, United States
References: 78
Accession Number: 2007-039039
Categories: Mineralogy of non-silicates
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 3 tables
Secondary Affiliation: University of Strathclyde, GBR, United KingdomUniversity of Glasgow, GBR, United KingdomSmithsonian Institution, USA, United StatesBrookhaven National Laboratory, USA, United States
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Abstract, copyright, Mineralogical Society of America. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 200721
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