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. http://resolver.caltech.edu/CaltechAUTHORS:20120830-094450477
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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.
|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.|
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|Deposited By:||Jason Perez|
|Deposited On:||30 Aug 2012 17:35|
|Last Modified:||23 Jul 2013 18:48|
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