Rietveld refinement of okayamalite, Ca2SiB2O7; structural evidence for the B/Si ordered distribution

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doi: 10.2138/am-2000-1023
Authors:Giuli, G.; Bindi, L.; Bonazzi, P.
Author Affiliations:Primary:
Universita di Firenze, Dipartimento di Scienze della Terra, Florence, Italy
Volume Title:American Mineralogist
Source:American Mineralogist, 85(10), p.1512-1515. Publisher: Mineralogical Society of America, Washington, DC, United States. ISSN: 0003-004X
Publication Date:2000
Note:In English. 27 refs.; illus., incl. 3 tables
Summary:The structure of okayamalite from Arendal, Norway, was refined using the Rietveld method, with CoKα powder X-ray diffraction data (RF = 3.69%). Okayamalite exhibits a melilite-type structure, space group P4̄21m, with cell edges a = 7.1248(2), c = 4.8177(2) Å. Si and B are ordered on the T1 and T2 sites respectively, in agreement with the refined tetrahedral distances ([T1-O] = 1.657 Å and [T2-O] = 1.498 Å). In comparison with the other melilite-type compounds, the cation population in okayamalite leads to the minimum structural misfit between tetrahedral and square-antiprism layers.
Sections:Crystal structure
Subsections:Specific structures: silicates
Subjects:Crystal chemistry; Crystal structure; Order-disorder; Oxides; Rietveld refinement; Unit cell; X-ray diffraction data; Arendal Norway; Europe; Norway; Scandinavia; Western Europe; Okayamalite
Abstract Numbers:01M/3776
Record ID:2001002763
Copyright Information:GeoRef, Copyright 2019 American Geosciences Institute.
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