A new dense silica polymorph: A possible link between tetrahedrally and octahedrally coordinated silica
Abstract
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.Additional details
- Eprint ID
- 33701
- Resolver ID
- CaltechAUTHORS:20120830-094450477
- NSF
- EAR-0207934
- NASA
- NAG5-10198
- 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
- Created
-
2012-08-30Created from EPrint's datestamp field
- Updated
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2020-03-09Created from EPrint's last_modified field
- Caltech groups
- Division of Geological and Planetary Sciences (GPS)
- Other Numbering System Name
- Caltech Division of Geological and Planetary Sciences
- Other Numbering System Identifier
- 8943