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seifertite

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Journal Article
Published: 01 January 2016
American Mineralogist (2016) 101 (1): 231–234.
...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...
FIGURES
Journal Article
Published: 01 January 2015
American Mineralogist (2015) 100 (1): 120–129.
...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...
FIGURES | View All (6)
Journal Article
Published: 01 October 2014
American Mineralogist (2014) 99 (10): 2035–2042.
...-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...
FIGURES | View All (6)
Journal Article
Published: 01 August 2008
European Journal of Mineralogy (2008) 20 (4): 523–528.
...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...
FIGURES
Image
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
Image
Phase boundaries for the β-stishovite to <span class="search-highlight">seifertite</span> and <span class="search-highlight">seifertite</span> 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
Journal Article
Published: 01 July 2020
American Mineralogist (2020) 105 (7): 1014–1020.
...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...
FIGURES | View All (6)
Image
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
Image
XRD data of <span class="search-highlight">seifertite</span> 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
Image
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
Image
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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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.
Image
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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(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
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(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
Equations of state for β-stishovite and <span class="search-highlight">seifertite</span>. 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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Raman spectra of stishovite ( a ), intergrowth of stishovite and <span class="search-highlight">seifertite</span>...
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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( 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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Band-to-band transitions at the Γ-points of the BZ at the direct gaps of ( ...
Published: 01 January 2015
Figure 1 Band-to-band transitions at the Γ-points of the BZ at the direct gaps of ( a ) seifertite (using Mulliken irreducible representation labels of the D 2h group), ( b ) stishovite (D 2h ), and ( c ) coesite (C 2h ). Green (red) arrows mark electric dipole allowed (forbidden) transitions
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Selected diffraction reflections from one grain of <span class="search-highlight">seifertite</span> 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