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Letter. Crystal chemistry of dense hydrous magnesium silicates: The structure of phase H, MgSiH2O4, synthesized at 45 GPa and 1000 °C

  • Luca Bindi EMAIL logo , Masayuki Nishi , Jun Tsuchiya and Tetsuo Irifune
Published/Copyright: August 12, 2014
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American Mineralogist
From the journal American Mineralogist Volume 99 Issue 8-9

Abstract

The crystal structure of the dense hydrous magnesium silicate phase H, MgSiH2O4, synthesized at 45 GPa and 1000 °C, was investigated by single-crystal X-ray diffraction. Although showing a deterioration process under the X-ray beam, the compound was found to be orthorhombic, space group Pnnm (CaCl2- type structure), with lattice parameters a = 4.733(2), b = 4.3250(10), c = 2.8420(10) Å, V = 58.18(3) Å3, and Z = 1. The structure was refined to R1 = 0.0387 using 53 observed reflections [2s(I) level]. Magnesium and silicon were found to be disordered at the same octahedral site (with a mean bond distance of 1.957 Å). Hydrogen was not located in the difference Fourier maps, but it is very likely disordered at a half-occupied 4g position. The centrosymmetric nature of the structure of phase H is examined in relation to that reported for pure d-AlOOH at ambient conditions (non-centrosymmetric, P21nm), and the possibility that these two compounds can form a solid solution at least at high pressure is discussed.

Keywords: Phase H; dense hydrous magnesium silicates; lower mantle; crystal structure; synthesis
Published Online: 2014-8-12
Published in Print: 2014-8-1

© 2014 by Walter de Gruyter Berlin/Boston

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https://doi.org/10.2138/am.2014.4994
Keywords for this article
Phase H; dense hydrous magnesium silicates; lower mantle; crystal structure; synthesis

Articles in the same Issue

  1. Chemistry and Mineralogy of Earth’s Mantle. Evidence for multiple diamondite-forming events in the mantle
  2. Chemistry and Mineralogy of Earth’s Mantle. Evidence for multiple diamondite-forming events in the mantle
  3. Chemistry and Mineralogy of Earth’s Mantle. Experimental determination of melting in the systems enstatite-magnesite and magnesite-calcite from 15 to 80 GPa
  4. Chemistry and Mineralogy of Earth’s Mantle. The spin state of iron in Fe3+-bearing Mg-perovskite and its crystal chemistry at high pressure
  5. Chemistry and Mineralogy of Earth’s Mantle. Hexagonal Na0.41[Na0.125Mg0.79Al0.085]2[Al0.79Si0.21]6O12 (NAL phase): Crystal structure refinement and elasticity
  6. What Lurks in the Martian Rocks and Soil? Investigations of Sulfates, Phosphates, and Perchlorates. Multivariate Analysis of Raman Spectra for the Identification of Sulfates: Implications for ExoMars
  7. What Lurks in the Martian Rocks and Soil? Investigations of Sulfates, Phosphates, and Perchlorates. Spectral and thermal properties of perchlorate salts and implications for Mars
  8. What Lurks in the Martian Rocks and Soil? Investigations of Sulfates, Phosphates, and Perchlorates. Reflectance spectroscopy and optical functions for hydrated Fe-sulfates
  9. Fluids in the Crust. Redox effects on calcite-portlandite-fluid equilibria at for earc conditions: Carbon mobility, methanogenesis, and reduction melting of calcite
  10. Fluids in the Crust. Constraints on the mobilization of Zr in magmatic-hydrothermal processes in subduction zones from in situ fluid-melt partitioning experiments
  11. The Second Conference on the Lunar Highlands Crust and New Directions. The petrogenesis of impact basin melt rocks in lunar meteorite Shişr 161
  12. Amorphous Materials: Properties, structure, and durability. The nearly complete dissociation of water in glasses with strong aluminum avoidance
  13. Sepiolite-palygorskite polysomatic series: Oriented aggregation as a crystal growth mechanism in natural environments
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  16. Characteristics of djerfisherite from fluid-rich, metasomatized alkaline intrusive environments and anhydrous enstatite chondrites and achondrites
  17. Ferroan geikielite and coupled spinel-rutile exsolution from titanohematite: Interface characterization and magnetic properties
  18. Constraints on the incorporation mechanism of chlorine in peralkaline and peraluminous Na2O-CaO-Al2O3-SiO2 glasses
  19. Interlayer structure model of tri-hydrated low-charge smectite by X-ray diffraction and Monte Carlo modeling in the Grand Canonical ensemble
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