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Neutron diffraction study of hydrogen in birnessite structures

Jeffrey E. Post, Peter J. Heaney and Yunchul Cho
Neutron diffraction study of hydrogen in birnessite structures
American Mineralogist (April 2011) 96 (4): 534-540

Abstract

The positions of hydrogen (deuterium) cations within the interlayer of synthetic Na- and K-birnessite samples have been determined for the first time using Rietveld analysis and Fourier difference syntheses, from time-of-flight powder neutron diffraction data. This study revealed that two symmetry-related D(H) positions are located approximately 1 Aa above and below the midpoint between the split O interlayer sites in Na-birnessite. This result confirms our earlier interpretation that the split interlayer sites include O atoms from two symmetrically equivalent H (sub 2) O molecules. These molecules are oriented 180 degrees to each other, and they are pivoted about a single set of H(D) atoms positions. The interlayer H (sub 2) O molecules in K-birnessite are oriented such that one of the H(D) atoms is pointed approximately toward the Mn octahedral layer O atoms and the other is directed approximately within the net of interlayer K/O sites. In K-birnessite, six K-O (sub oct) distances are shorter than 3.35 Aa, compared with only two Na-O (sub oct) bond lengths in Na-birnessite, suggesting that K cations are more tightly bonded to the octahedral O atoms than are Na cations.


ISSN: 0003-004X
EISSN: 1945-3027
Coden: AMMIAY
Serial Title: American Mineralogist
Serial Volume: 96
Serial Issue: 4
Title: Neutron diffraction study of hydrogen in birnessite structures
Affiliation: Smithsonian Institution, Department of Mineral Sciences, Washington, DC, United States
Pages: 534-540
Published: 201104
Text Language: English
Publisher: Mineralogical Society of America, Washington, DC, United States
References: 30
Accession Number: 2011-036739
Categories: Mineralogy of non-silicates
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 3 tables
Secondary Affiliation: Pennsylvania State University, 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: 201121
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