Crystal structure of a new high-pressure polymorph of topaz-OH

Masami Kanzaki

doi:10.2138/am.2010.3555

Crystal structure of a new high-pressure polymorph of topaz-OH

Masami Kanzaki

Institute for Planetary Materials

Research output: Contribution to journal › Article › peer-review

13 Citations (Scopus)

Abstract

A new high-pressure form of topaz-OH (denoted here topaz-OH II) was obtained at 14 GPa and 1400 °C. The X-ray diffraction patternof this phase can be indexed by an orthorhombic cell with a = 4.72318(5), b = 8.91480(9), and c = 2.77276(3) Å. The lengths of a andb are similar, but c is approximately a third of that for a previously reported topaz-OH (denoted topaz-OH I). The structural formula of topaz-OH II can be written as (Al _0.68Si_0.32(O_0.66(OH)_0.34) ₂, suggesting significant cation disorder in the structure. The crystal structure of topaz-OH II is solved using powder synchrotron X-ray diffraction data, and refined with constraints provided by a separate multi-nuclear NMR study. The structure has similarities with topaz-OH I and diaspore (α-AlOOH) structures, having partially occupied double edge-shared octahedral chains, and 2 × 1 tunnels with partially occupied tetrahedral and octahedral sites.

Original language	English
Pages (from-to)	1349-1352
Number of pages	4
Journal	American Mineralogist
Volume	95
Issue number	8-9
DOIs	https://doi.org/10.2138/am.2010.3555
Publication status	Published - Aug 1 2010

Keywords

Crystal structure
High-pressure studies
Order-disorder
Phase transition

ASJC Scopus subject areas

Geophysics
Geochemistry and Petrology

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title = "Crystal structure of a new high-pressure polymorph of topaz-OH",

abstract = "A new high-pressure form of topaz-OH (denoted here topaz-OH II) was obtained at 14 GPa and 1400 °C. The X-ray diffraction patternof this phase can be indexed by an orthorhombic cell with a = 4.72318(5), b = 8.91480(9), and c = 2.77276(3) {\AA}. The lengths of a andb are similar, but c is approximately a third of that for a previously reported topaz-OH (denoted topaz-OH I). The structural formula of topaz-OH II can be written as (Al 0.68Si0.32(O0.66(OH)0.34) 2, suggesting significant cation disorder in the structure. The crystal structure of topaz-OH II is solved using powder synchrotron X-ray diffraction data, and refined with constraints provided by a separate multi-nuclear NMR study. The structure has similarities with topaz-OH I and diaspore (α-AlOOH) structures, having partially occupied double edge-shared octahedral chains, and 2 × 1 tunnels with partially occupied tetrahedral and octahedral sites.",

keywords = "Crystal structure, High-pressure studies, Order-disorder, Phase transition",

author = "Masami Kanzaki",

year = "2010",

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language = "English",

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AB - A new high-pressure form of topaz-OH (denoted here topaz-OH II) was obtained at 14 GPa and 1400 °C. The X-ray diffraction patternof this phase can be indexed by an orthorhombic cell with a = 4.72318(5), b = 8.91480(9), and c = 2.77276(3) Å. The lengths of a andb are similar, but c is approximately a third of that for a previously reported topaz-OH (denoted topaz-OH I). The structural formula of topaz-OH II can be written as (Al 0.68Si0.32(O0.66(OH)0.34) 2, suggesting significant cation disorder in the structure. The crystal structure of topaz-OH II is solved using powder synchrotron X-ray diffraction data, and refined with constraints provided by a separate multi-nuclear NMR study. The structure has similarities with topaz-OH I and diaspore (α-AlOOH) structures, having partially occupied double edge-shared octahedral chains, and 2 × 1 tunnels with partially occupied tetrahedral and octahedral sites.

KW - Crystal structure

KW - High-pressure studies

KW - Order-disorder

KW - Phase transition

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Crystal structure of a new high-pressure polymorph of topaz-OH

Abstract

Keywords

ASJC Scopus subject areas

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