Location of hydrogen atoms in hydronium jarosite

Spratt, Henry J., Avdeev, Maxim, Pfrunder, Michael C., McMurtrie, John, Rintoul, Llew and Martens, Wayde N. (2014) Location of hydrogen atoms in hydronium jarosite. Physics and Chemistry of Minerals, 41 7: 505-517. doi:10.1007/s00269-014-0661-5

Author Spratt, Henry J.
Avdeev, Maxim
Pfrunder, Michael C.
McMurtrie, John
Rintoul, Llew
Martens, Wayde N.
Title Location of hydrogen atoms in hydronium jarosite
Journal name Physics and Chemistry of Minerals   Check publisher's open access policy
ISSN 1432-2021
Publication date 2014-07-01
Year available 2014
Sub-type Article (original research)
DOI 10.1007/s00269-014-0661-5
Volume 41
Issue 7
Start page 505
End page 517
Total pages 13
Place of publication Heidelberg Germany
Publisher Springer
Language eng
Formatted abstract
Various models for the crystal structure of hydronium jarosite were determined from Rietveld refinements against neutron powder diffraction patterns collected at ambient temperature and also single-crystal X-ray diffraction data. The possibility of a lower symmetry space group for hydronium jarosite that has been suggested by the literature was investigated. It was found the space group is best described as R3m, the same for other jarosite minerals. The hydronium oxygen atom was found to occupy the 3m site (3a Wyckoff site). Inadequately refined hydronium bond angles and bond distances without the use of restraints are due to thermal motion and disorder of the hydronium hydrogen atoms across numerous orientations. However, the acquired data do not permit a precise determination of these orientations; the main feature up/down disorder of hydronium is clear. Thus, the highest symmetry model with the least disorder necessary to explain all data was chosen: The hydronium hydrogen atoms were modeled to occupy an m (18 h Wyckoff site) with 50 % fractional occupancy, leading to disorder across two orientations. A rigid body description of the hydronium ion rotated by 60° with H-O-H bond angles of 112° and O-H distances of 0.96 Å was optimal. This rigid body refinement suggests that hydrogen bonds between hydronium hydrogen atoms and basal sulfate oxygen atoms are not predominant. Instead, hydrogen bonds are formed between hydronium hydrogen atoms and hydroxyl oxygen atoms. The structure of hydronium alunite is expected to be similar given that alunite supergroup minerals are isostructural.
Keyword Crystal structure
Hydrogen location
Hydronium jarosite
Neutron diffraction
Orientational disorder
Rietveld refinement
Q-Index Code C1
Q-Index Status Provisional Code
Institutional Status Non-UQ

Document type: Journal Article
Sub-type: Article (original research)
Collections: Non HERDC
School of Chemistry and Molecular Biosciences
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