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New structure of high-pressure body-centered orthorhombic Fe<sub>2</sub>SiO<sub>4</sub> [electronic resource].

Published
Washington, D.C. : United States. National Nuclear Security Administration, 2015.
Oak Ridge, Tenn. : Distributed by the Office of Scientific and Technical Information, U.S. Dept. of Energy
Physical Description
pages 1,736-1,743 : digital, PDF file
Additional Creators
United States. National Nuclear Security Administration and United States. Department of Energy. Office of Scientific and Technical Information
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Summary
Here, a structural change in Fe2SiO4 spinel and the structure of a new high pressure phase are determined by Rietveld 26 profile fitting of x-ray diffraction data up to 64 GPa at ambient temperature. The compression curve of the spinel is discontinuous at approximately 20 GPa. Fe Kβ x-ray emission measurements at high pressure show that the transition from a high spin (HS) to an intermediate spin (IS) state begins at 17 GPa in the spinel phase. The IS electronic state is gradually enhanced with pressure, which results in an isostructural phase transition. A transition from the cubic spinel structure to a body centered orthorhombic phase (I-Fe2SiO4) with space group Imma and Z=4 was observed at approximately 34 GPa. The structure of I-Fe2SiO4 has two crystallographically distinct FeO6 octahedra, which are arranged in layers parallel to (101) and (011) and are very similar to the layers of FeO6 octahedra that constitute the spinel structure. Silicon also exists in six-fold coordination in I-Fe2SiO4. The transformation to the new high-pressure phase is reversible under decompression at ambient temperature. A Martensitic transformation of each slab of the spinel structure with translation vector [$\vec{1/8}$ $\vec{1/8}$ $\vec{1/8}$] generates the I-Fe2SiO4 structure. Laser heating of I-Fe2SiO4 at 1500 K results in a decomposition of the material to rhombohedral FeO and SiO2 stishovite.
Report Numbers
E 1.99:1335457
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Note
Published through SciTech Connect.
08/01/2015.
American Mineralogist 100 8-9 ISSN 0003-004X AM
Takamitsu Yamanaka; Atsushi Kyono; Yuki Nakamoto; Svetlana Kharlamova; Viktor V. Struzhkin; Stephen A. Gramsch; Ho-kwang Mao; Russell J. Hemley.
Carnegie Institution of Washington, Washington, D.C. (United States)
Funding Information
NA0002006
View MARC record | catkey: 24494241