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seifertite

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Journal Article

In-situ crystal structure determination of seifertite SiO 2 at 129 GPa: Studying a minor phase near Earth’s core–mantle boundary

Li Zhang, Dmitry Popov, Yue Meng, Junyue Wang, Cheng Ji, Bing Li, Ho-kwang Mao
Published: 01 January 2016
American Mineralogist (2016) 101 (1): 231–234.
DOI: https://doi.org/10.2138/am-2016-5525
...Li Zhang; Dmitry Popov; Yue Meng; Junyue Wang; Cheng Ji; Bing Li; Ho-kwang Mao Abstract Seifertite SiO 2 likely exists as a minor phase near the core–mantle boundary. By simulating the pressure and temperature conditions near the core–mantle boundary, seifertite was synthesized as a minor phase...
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Optical absorption anisotropy of high-density, wide-gap, high-hardness SiO 2 polymorphs seifertite, stishovite, and coesite

Kamil Klier, Jeffery A. Spirko, Kai M. Landskron
Published: 01 January 2015
American Mineralogist (2015) 100 (1): 120–129.
DOI: https://doi.org/10.2138/am-2015-4890
...Kamil Klier; Jeffery A. Spirko; Kai M. Landskron Abstract Dense, high-refractive index, ultra-hard, wide-gap polymorphs of SiO 2 , recently discovered orthorhombic seifertite (space group 60 Pbcn ), and earlier characterized tetragonal stishovite (space group 136 P 42/ mnm ) and monoclinic coesite...
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Journal Article

Phase diagram and P-V-T equation of state of Al-bearing seifertite at lowermost mantle conditions

Denis Andrault, Reidar G. Trønnes, Zuzana Konôpková, Wolfgang Morgenroth, Hanns P. Liermann, Guillaume Morard, Mohamed Mezouar
Published: 01 October 2014
American Mineralogist (2014) 99 (10): 2035–2042.
DOI: https://doi.org/10.2138/am-2014-4697
...-heated diamond-anvil cell coupled with synchrotron-based in situ X-ray diffraction. The phase transition from CaCl 2 -structured to α-PbO 2 -structured (seifertite) polymorphs occurs between 113 and 119 GPa at 2500 K. The range of pressure where the two phases coexist is small. There is a slight decrease...
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Seifertite, a dense orthorhombic polymorph of silica from the Martian meteorites Shergotty and Zagami

Ahmed El Goresy, Przemyslaw Dera, Thomas G. Sharp, Charles T. Prewitt, Ming Chen, Leonid Dubrovinsky, Brigitte Wopenka, Nabil Z. Boctor, Russell J. Hemley
Published: 01 August 2008
European Journal of Mineralogy (2008) 20 (4): 523–528.
DOI: https://doi.org/10.1127/0935-1221/2008/0020-1812
...Ahmed El Goresy; Przemyslaw Dera; Thomas G. Sharp; Charles T. Prewitt; Ming Chen; Leonid Dubrovinsky; Brigitte Wopenka; Nabil Z. Boctor; Russell J. Hemley Abstract Seifertite is a dense orthorhombic polymorph of silica with the scrutinyite (α-PbO 2 ) type structure that was found as lamellae...
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Phase boundaries for the β-stishovite to <span class="search-highlight">seifertite</span> and <span class="search-highlight">seifertite</span> to pyrit...

Phase boundaries for the β-stishovite to seifertite and seifertite to pyrit...

Published: 01 July 2020
Figure 4. Phase boundaries for the β-stishovite to seifertite and seifertite to pyrite-structured silica. The present results are displayed together with previous results (dashed and solid lines represent experimental and theoretical results, respectively). Static transition pressures are without
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Gibbs free energy change upon the phase transition from β-stishovite to sei...

Gibbs free energy change upon the phase transition from β-stishovite to sei...

Published: 01 July 2020
Figure 2. Gibbs free energy change upon the phase transition from β-stishovite to seifertite (upper panel) and seifertite to pyrite-type silica (lower) as a function of pressure (contour values in GPa) and temperature, calculated with the GGA functional. The transition pressure increases
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XRD data of <span class="search-highlight">seifertite</span> at 129 GPa and after T quench (X-ray wavelength of...

XRD data of seifertite at 129 GPa and after T quench (X-ray wavelength of...

Published: 01 January 2016
Figure 1 XRD data of seifertite at 129 GPa and after T quench (X-ray wavelength of 0.3738 Å). ( a ) A representative spotty XRD pattern of seifertite coexisting with the dominant phase pPv at a fixed rotation angle. S = silica, pPv = post-perovskite, Ne = neon. ( b ) An integrated powder
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Selected regions of the 2D diffraction image (upper frames) and its spectra...

Selected regions of the 2D diffraction image (upper frames) and its spectra...

Published: 01 October 2014
Figure 1 Selected regions of the 2D diffraction image (upper frames) and its spectral integration (lower frame) recorded in situ at 120 GPa and 2500 K. Regions where major seifertite diffraction peaks occur are colored in red. The number of seifertite crystallites is insufficient for a full
Journal Article

High-pressure silica phase transitions: Implications for deep mantle dynamics and silica crystallization in the protocore

Pratik Kr. Das, Chris E. Mohn, John P. Brodholt, Reidar G. Trønnes
Published: 01 July 2020
American Mineralogist (2020) 105 (7): 1014–1020.
DOI: https://doi.org/10.2138/am-2020-7299
...Figure 4. Phase boundaries for the β-stishovite to seifertite and seifertite to pyrite-structured silica. The present results are displayed together with previous results (dashed and solid lines represent experimental and theoretical results, respectively). Static transition pressures are without...
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The diffraction spectra are refined in two steps. We first perform a full X...

The diffraction spectra are refined in two steps. We first perform a full X...

Published: 01 October 2014
Figure 2 The diffraction spectra are refined in two steps. We first perform a full X-ray profile refinement, using the Rietveld mode and the structural model of seifertite (upper frames). Differences between experimental and calculated peak intensities are due to (1) change with pressure
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Density of silica phases calculated by the BurnMan code ( Cottaar et al. 20...

Density of silica phases calculated by the BurnMan code ( Cottaar et al. 20...

Published: 01 July 2020
Figure 6. Density of silica phases calculated by the BurnMan code ( Cottaar et al. 2014 ) along the default adiabat of Brown and Shankland (1981) , extended to 136 GPa and about 2450 K. Our predicted density for seifertite is 1.5% lower than the HeFESTo-value of Stixrude and Lithgow-Bertelloni
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XRD patterns [λ = 0.41360(7) Å] of a silica grain including stishovite and ...

XRD patterns [λ = 0.41360(7) Å] of a silica grain including stishovite and ...

Published: 01 May 2015
Figure 2 XRD patterns [λ = 0.41360(7) Å] of a silica grain including stishovite and seifertite. Sti = stishovite, α-PbO 2 = seifertite, Tr = tridymite.
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(A) Backscattered electron (BSE) micrograph of a triangular dense silica gr...

(A) Backscattered electron (BSE) micrograph of a triangular dense silica gr...

Published: 01 August 2008
Fig. 1. (A) Backscattered electron (BSE) micrograph of a triangular dense silica grain from the Shergotty meteorite. The grain consists of numerous domains of a maximum diameter of 60 μ m. Each domain displays an orthogonal pattern of bright (seifertite) and dark (dense SiO 2 glass) lamellae
Image
(A) Backscattered electron (BSE) micrograph of a triangular dense silica gr...

(A) Backscattered electron (BSE) micrograph of a triangular dense silica gr...

Published: 01 August 2008
Fig. 1. (A) Backscattered electron (BSE) micrograph of a triangular dense silica grain from the Shergotty meteorite. The grain consists of numerous domains of a maximum diameter of 60 μ m. Each domain displays an orthogonal pattern of bright (seifertite) and dark (dense SiO 2 glass) lamellae
Image
Enthalpy change upon the phase transition from ( a ) β-stishovite to seifer...

Enthalpy change upon the phase transition from ( a ) β-stishovite to seifer...

Published: 01 July 2020
Figure 1. Enthalpy change upon the phase transition from ( a ) β-stishovite to seifertite and ( b ) seifertite to pyrite-type silica as a function of pressure in the static limit, determined using the GGA-PBE (red) and HSE06 (blue) functionals. (Color online.)
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Equations of state for β-stishovite and <span class="search-highlight">seifertite</span>. The HSE06-based EoS (ad...

Equations of state for β-stishovite and seifertite. The HSE06-based EoS (ad...

Published: 01 July 2020
Figure 5. Equations of state for β-stishovite and seifertite. The HSE06-based EoS (adjusted to 300 K by adding the GGA-derived volume increase from 0 to 300 K) is similar to the 300 K experimental data of Grocholski et al. (2013) , Murakami et al. (2003) and Fischer et al. (2018) . The LDA
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( a ) Volumes of the two silica polymorphs measured around the transition p...

( a ) Volumes of the two silica polymorphs measured around the transition p...

Published: 01 October 2014
-bearing SiO 2 glass with 4 wt% Al 2 O 3 (black dotted line: Bolfan-Casanova et al. 2009 ). Closed and open symbols represent the CaCl 2 -phase and seifertite, respectively. ( b ) High-temperature volumes (red circles) recorded for seifertite from 100 to 162 GPa and up to 4300 K. We report
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Raman spectra of stishovite ( a ), intergrowth of stishovite and <span class="search-highlight">seifertite</span>...

Raman spectra of stishovite ( a ), intergrowth of stishovite and seifertite...

Published: 01 June 2022
Figure 3. Raman spectra of stishovite ( a ), intergrowth of stishovite and seifertite ( b ), tuite ( c ), apatite ( d ), and host pyroxene ( e ) marked in Figure 2 .
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Selected diffraction reflections from one grain of <span class="search-highlight">seifertite</span> are shown in ...

Selected diffraction reflections from one grain of seifertite are shown in ...

Published: 01 January 2016
Figure 2 Selected diffraction reflections from one grain of seifertite are shown in the middle within 30 × 30 pixels (pixel size: 79 μm) at 129 GPa. ( a – b ) The multigrain method distinguishes a pair of {302} reflections from another pair of {321} with close d -spacing. ( c ) A pair of weak
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Band structure and optical absorption of <span class="search-highlight">seifertite</span>. ( left ) Energy band s...

Band structure and optical absorption of seifertite. ( left ) Energy band s...

Published: 01 January 2015
Figure 2 Band structure and optical absorption of seifertite. ( left ) Energy band structure in the momentum space. Symbols for special points of the Brillouin zone are given in caption to Figure A1-2 in Appendix 1 1 . Sizes of heavier plotting are given in parentheses with O2p-orbitals