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Rietveld structure refinement of MgGeO3 post-perovskite phase to 1 Mbar
-
Atsushi Kubo
,
Vitali B. Prakapenka
Veröffentlicht/Copyright:
1. April 2015
Abstract
Using the CaIrO3-type structure model (space group Cmcm), lattice parameters and atomic positions of the MgGeO3 post-perovskite (pPv) phase were determined based on Rietveld refinements at 78-109 GPa and first-principles calculations based on density functional theory. The reproducibility of structural parameters obtained for different samples, consistency with theoretical calculations, and good agreement with expected bond lengths based on structurally similar materials all provide evidence for both validity of CaIrO3-type structure model for the pPv phase in MgGeO3 exceeding 1 Mbar and reliability of structural parameters obtained by Rietveld refinements approaching 1 Mbar. The MgGeO3 pPv phase exhibits strong anisotropy in axial compressibility, with the b-axis being most compressible. The polyhedral bulk modulus for the GeO6 octahedron is 1.9× larger than that for the MgO8 hendecahedron. Examination of neighboring O-O distances shows that the O-O distance aligned along the a direction is one of the longest and that aligned along c is one of the shortest, and these may be related to the lower compressibility along c compared with a. Comparison of structural features of MgGeO3 pPv with those for MgSiO3, NaMgF3, and CaIrO3 pPv show that MgSiO3 pPv has more similarity with NaMgF3 and MgGeO3 pPv than with CaIrO3 pPv in such parameters as degree of octahedral distortion, implying that both NaMgF3 and MgGeO3 pPv are better analogs to MgSiO3 pPv than CaIrO3 pPv.
Keywords : Post-perovskite; MgGeO3; Rietveld refinement; high-pressure experiment; firstprinciples calculation; laser-heated diamond anvil cell; density functional theory; polycrystalline X-ray diffraction
Received: 2007-5-9
Accepted: 2008-1-30
Published Online: 2015-4-1
Published in Print: 2008-7-1
© 2015 by Walter de Gruyter Berlin/Boston
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Schlagwörter für diesen Artikel
Post-perovskite;
MgGeO3;
Rietveld refinement;
high-pressure experiment;
firstprinciples calculation;
laser-heated diamond anvil cell;
density functional theory;
polycrystalline X-ray diffraction
Artikel in diesem Heft
- Rietveld structure refinement of MgGeO3 post-perovskite phase to 1 Mbar
- High-temperature ammonium white mica from the Betic Cordillera (Spain)
- Synthesis and crystal structure of the feldspathoid CsAlSiO4: An open-framework silicate and potential nuclear waste disposal phase
- The crystal chemistry of Li in gadolinite
- The effect of the hedenbergitic substitution on the compressibility of jadeite
- The structure of monohydrocalcite and the phase composition of the beachrock deposits of Lake Butler and Lake Fellmongery, South Australia
- First-principles calculation of the infrared spectrum of hematite
- In situ observations of muscovite dissolution under alkaline conditions at 25–50 °C by AFM with an air/fluid heater system
- Ramanite-(Cs) and ramanite-(Rb): New cesium and rubidium pentaborate tetrahydrate minerals identified with Raman spectroscopy
- Pressure-temperature studies of talc plus water using X-ray diffraction
- Hematite and magnetite precipitates in olivine from the Sulu peridotite: A result of dehydrogenation-oxidation reaction of mantle olivine?
- Arsenide in a metasomatized peridotite xenolith as a constraint on arsenic behavior in the mantle wedge
- Multiple oxygen sites in synthetic phyllosilicates with expandable layers: 17O solid-state NMR study
- On the existence of a Na-deficient monoclinic trinepheline with composition Na7.85Al7.85Si8.15O32
- Chlorite and biotite weathering, Fe2+-rich corrensite formation, and Fe behavior under low Po₂ conditions and their implication for Precambrian weathering
- Structural characterization of natural UO2 at pressures up to 82 GPa and temperatures up to 2200 K
- Dense hydrous magnesium silicates, phase D, and superhydrous B: New structural constraints from one- and two-dimensional 29Si and 1H NMR
- Mid-IR bands of synthetic calcic amphiboles of tremolite-pargasite series and of natural calcic amphiboles
- Probing the site occupancies of Co-, Ni-, and Mn-substituted biogenic magnetite using XAS and XMCD
- Origin of titanite in metarodingite from the Zagros Thrust Zone, Iraq
- Experimental calibration of aluminum partitioning between olivine and spinel as a geothermometer
- Single-crystal X-ray diffraction study of CaIrO3
- Orthorhombic polymorph of rengeite from Ohmi region, central Japan
- New insights into the crystal chemistry of epididymite and eudidymite from Malosa, Malawi: A single-crystal neutron diffraction study
- Mechanisms of rhyolitic glass hydration below the glass transition
- Heat capacity and entropy of melanophlogite: Molecule-containing porosils in nature
- Crystal structure of glaucodot, (Co,Fe)AsS, and its relationships to marcasite and arsenopyrite
- Modification of gas speciation in quartz-hosted fluid inclusions by stray laser radiation during LA-ICPMS analysis
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