Abstract
The positions of H in Al2SiO4(OH)2, the fully hydrated high-pressure synthetic analogue of topaz have been determined from single-crystal XRD. Two nonequivalent H positions, approximately 2.4 Å apart, were located. The H sites are significantly displaced from the single one found in natural OH-bearing fluor-topaz and violate the mirror plane of space group Pbnm, at least locally. Each H is associated with three O atoms in an irregular trifurcated H-bond arrangement. These results provide an explanation for observations of split OH-stretching bands in infrared spectra, as well as for the uniform dilatation observed for both the [6]Al and [4]Si polyhedra relative to those in fluor-topaz. -from Authors
Original language | English (US) |
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Pages (from-to) | 401-404 |
Number of pages | 4 |
Journal | American Mineralogist |
Volume | 79 |
Issue number | 3-4 |
State | Published - Jan 1 1994 |
Externally published | Yes |
ASJC Scopus subject areas
- Geophysics
- Geochemistry and Petrology