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A new dense silica polymorph: A possible link between tetrahedrally and octahedrally coordinated silica

Luo, Sheng-Nian and Tschauner, Oliver and Ahrens, Thomas J. and Asimow, Paul D. (2004) A new dense silica polymorph: A possible link between tetrahedrally and octahedrally coordinated silica. American Mineralogist, 89 (2-3). pp. 455-461. ISSN 0003-004X.

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We present the discovery of a novel dense silica polymorph retrieved from shock-wave and diamond-anvil cell experiments. This polymorph is the first observed silicate composed of face-sharing polyhedra and it has a density similar to stishovite. Sterical constraints on the bond angles induce an intrinsic disorder of Si positions, such that the Si-coordination is transitional between four-and sixfold. The structure provides a mechanism for this coordination change in silica and other silicates at high temperature that is fundamentally different from mechanisms at 300 K. The new polymorph also illustrates how the face-sharing polyhedra, naturally occurring along previously proposed compression mechanisms for dense silicate melts, can be constructed without inferring unphysically small bond angles.

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Asimow, Paul D.0000-0001-6025-8925
Additional Information:© 2004 Mineralogical Society of America. Manuscript Received August 5, 2003; manuscript Accepted November 17, 2003. This work was supported by NSF Grant EAR-0207934 and NASA Grant NAG5-10198. S.N.L. was also sponsored by a Director’s Post-doctoral Fellowship at Los Alamos National Laboratory (P-24 and EES-11). O.T. also acknowledges support from NNSA Cooperative Agreement DE-FC88-01NV14049. We appreciate the help of G.R. Rossman and E. Arredondo in Raman spectroscopy, P. Dera, C. Prewitt, R.J. Hemley, and H.K. Mao for kind permission to use their X-ray diffraction and CO2-laser heating facilities. We thank P. Dera and two anonymous reviewers for helpful comments. Contribution no. 8943, Division of Geological and Planetary Sciences, California Institute of Technology.
Funding AgencyGrant Number
Los Alamos National Laboratory Director's Postdoctoral Fellowship P-24
Los Alamos National Laboratory Director's Postdoctoral Fellowship EES-11
NNSA Cooperative Agreement DE-FC88-01NV14049
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Caltech Division of Geological and Planetary Sciences8943
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ID Code:33701
Deposited By: Jason Perez
Deposited On:30 Aug 2012 17:35
Last Modified:23 Jul 2013 18:48

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