H positions in leucophoenicite, Mn7Si3O12(OH)2; a close relative of the hydrous B phases

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doi: 10.2138/am-2002-0116
Authors:Welch, Mark D.; Marshall, William G.; Ross, Nancy L.; Knight, Kevin S.
Author Affiliations:Primary:
Natural History Museum, Department of Mineralogy, London, United Kingdom
Other:
Rutherford Appleton Laboratory, United Kingdom
Virginia Polytechnic Institute and State University, United States
Volume Title:American Mineralogist
Source:American Mineralogist, 87(1), p.154-159. Publisher: Mineralogical Society of America, Washington, DC, United States. ISSN: 0003-004X
Publication Date:2002
Note:In English. 18 refs.; illus., incl. 4 tables
Summary:The proton positions in leucophoenicite, ideally Mn7Si3O12(OH)2, have been determined by neutron powder diffraction under ambient conditions on a natural sample from Franklin, New Jersey. Refinement in the P21/a space group gave RP = 2.0%), (wRp = 2.1%), χ2 = 4.04 for 110 refined parameters. The two non-equivalent protons form a pair of hydroxyl groups and make hydrogen bonds to the same O7 atom of the Sil tetrahedron at distances of 1.99(1) and 2.09(1) Å. The H....H distance in leucophoenicite is 2.16(1) Å, which is more than twice the Van der Waal's radius of H (>2 Å) and so no proton positional disorder is expected in leucophoenicite. A comparison of the H environments is made between leucophoenicite and Phase B, Superhydrous B, and Phase A.
Sections:Crystal structure
Subsections:Specific structures: silicates
Subjects:Behavior; Coordination; Crystal chemistry; Crystal structure; Elasticity; Formula; Mantle; Neutron diffraction data; Physical properties; Refinement; Rheology; Silicates; Space groups; New Jersey; United States; Leucophoenicite
Abstract Numbers:02M/2544
Record ID:2002020530
Copyright Information:GeoRef, Copyright 2019 American Geosciences Institute.
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