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Hydrogen-atom positions in P4/nnc vesuvianite

Lager, George A. and Xie, Qianyen and Ross, Fred K. and Rossman, George R. and Armbruster, Thomas and Rotella, Frank J. and Schultz, Arthur J. (1999) Hydrogen-atom positions in P4/nnc vesuvianite. Canadian Mineralogist, 37 (3). pp. 763-768. ISSN 0008-4476.

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The crystal structure of a large crystal (11.0 x 7.8 x 4.1 nm) of gem-quality Fe-bearing vesuvianite [ɑ 15.533 (ll), c 11.785(16) Å, V 2843(5) Å^3; є 1.713(5), to ω 1.710(5), 2V 0°(5);D 3.43 g cm^(-3); 3.68 wt%FeO] from Kenya has been refined at 298 K by single-crystal neutron-diffraction methods to a weighted R value of 3.9% for 1448 unique Bragg reflections. No violations of P4/nnc space-group symmetry were observed on examination of the crystal by time-of-flight neutron methods. The protons are associated with oxygen atoms O(11)[H(1)0.4592(7),0.4814(9),0.3083(8)]and O(10)[H(2)0.25,0.25,0.280(10), as predicted by bond-valence calculations. Difference-Fourier maps show a double minimum between adjacent O(10) atoms along c, indicating a statistical distribution of H(2) between two sites. The partial occupancy of the H(1) site (85%) is consistent with the substitution of fluorine for oxygen at the O(11) site. Although hydrogrossular and vesuvianite have similar structures and occur in many of the same environments, the neutron-diffraction results rule out the possibility of a hydrogarnet-type substitution [(O_4H_4)^4 = (SiO_4)^(4-)] in this specimen. Its infrared spectrum (6500-7500 cm^(-1)) most closely resembles that of intermediate fluorine, boron-poor vesuvianite.

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Rossman, George R.0000-0002-4571-6884
Additional Information:© 1999 Mineralogical Association of Canada. Received August 17, 1998, revised manuscript accepted March 1, 1999. Support of this work was provided by the National Science Foundation through grant EAR-8719848 to GAL and grants EAR-8916064 and EAR-9218980 to GRR. Work performed at Argonne National Laboratory is supported by the U.S. DOE, Basic Energy Sciences under contract no. W-31-109-ENG-38. The authors thank the Gemological Institute of America for loaning this specimen to us, Frank C. Hawthome (Winnipeg) for providing sample "GEM", and Campbell Bridges (Nairobi) for assistance in establishing the probable origin of our vesuvianite specimen. Reviews by Lee A. Groat (Univ. of British Columbia), Mario Tribaudino (Univ. of Torino) and Peter C. Burns (Univ. of Notre Dame) significantly improved the manuscript.
Group:UNSPECIFIED, UNSPECIFIED, Division of Geological and Planetary Sciences
Funding AgencyGrant Number
Department of Energy (DOE) Basic Energy Sciences (BES)W-31-109-ENG-38
Subject Keywords:vesuvianite, crystal-structure refinement, neutron diffraction, hydrogen atoms
Issue or Number:3
Record Number:CaltechAUTHORS:20130501-142344280
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Official Citation: G. A. Lager, Qianyen Xie, F. K. Ross, G. R. Rossman, T. Armbruster, F. J. Rotella, and A. J. Schultz Hydrogen-atom positions in P4/nnc vesuvianite Can Mineral, June 1999, v. 37, p. 763-768
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:38215
Deposited By: Ruth Sustaita
Deposited On:01 May 2013 22:03
Last Modified:03 Oct 2019 04:55

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