Stolper, Edward M. and Ahrens, Thomas J.
On the nature of pressure‐induced coordination changes in silicate melts and glasses.
Geophysical Research Letters, 14
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Progressive decreases in the Si‐O‐Si angles between corner‐shared silicate tetrahedra in glasses and melts with increasing pressure can lead to arrangements of oxygen atoms that can be described in terms of edge‐ or face‐shared octahedra. This mechanism of compression can account for the gradual, continuous increases in melt and glass densities from values at low pressure that indicate dominantly tetrahedral coordination of Si to values at several tens of GPa that suggest higher coordination. It also can explain the unquenchable nature of octahedrally coordinated Si in glasses, the absence of spectroscopically detectable octahedrally coordinated Si in glasses until they are highly compressed, the gradual and reversible transformation from tetrahedral to octahedral coordination in glasses once the transformation is detectable spectroscopically, and the fact that this transformation takes place in glass at room temperature. It may also have relevance to pressure‐induced transformations from crystalline to glassy phases, the difficulty in retrieving some metastable high pressure crystalline phases at low pressure, and the observed differences between the pressures required for phase transformations in shock wave experiments on glasses and crystals.
|Additional Information:||© 1987 American Geophysical Union.
Received 15 May 1987; accepted 25 September 1987.
Acknowledgments. We thank J. Bass, G . E. Brown, Jr., R. Jeanloz, and Q. Williams for suggestions that helped us to develop the ideas presented in this paper, and R. Hemley, J. Holloway, and C . Meade for comments and reviews. We also thank R. Myers for assistance with the computer-generated graphics. This work was supported by NSF Grants EAR-8407784 and EAR-8618545. Caltech Division of Geological and Planetary Sciences Contribution 4471.|
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|Caltech Division of Geological and Planetary Sciences||4471|
|Official Citation:||Stolper, E. M. and T. J. Ahrens (1987), On the nature of pressure‐induced coordination changes in silicate melts and glasses, Geophys. Res. Lett., 14(12), 1231–1233, doi:10.1029/GL014i012p01231.|
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|Deposited On:||20 Aug 2012 20:11|
|Last Modified:||09 Dec 2016 20:47|
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