High resolution three‐dimensional X‐ray diffraction study of dislocations in grains of MgGeO<sub>3</sub> post‐perovskite at 90 GPa

Nisr, Carole; Ribárik, Gabor; Ungár, Tamás; Vaughan, Gavin; Cordier, Patrick; Merkel, Sébastien

doi:10.1029/2011jb008401

Cited by 47 publications

(33 citation statements)

References 59 publications

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“…With the precise structural determination enabled by the multigrain approach, it is anticipated that many previously determined HP structures will be revisited with the technique. For example, a new hexagonally structured (Mg,Fe)SiO3 phase has been discovered at a pressure range of 95-108 GPa [194], suggesting that the lower mantle may contain previously unidentified major phases; dislocations in grains of MgGeO3 post-bridgmanite has been determined at 90 GPa [371]; the crystal structure of seifertite (SiO2) as a minor phase in a sample at 129 GPa has been refined [167].…”

Section: Hp Crystallographymentioning

confidence: 99%

High-pressure studies with x-rays using diamond anvil cells

2016

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Pressure profoundly alters all states of matter. The symbiotic development of ultrahighpressure diamond anvil cells, to compress samples to sustainable multi-megabar pressures; and synchrotron x-ray techniques, to probe materials' properties in situ, has enabled the exploration of rich high-pressure (HP) science. In this article, we first introduce the essential concept of diamond anvil cell technology, together with recent developments and its integration with other extreme environments. We then provide an overview of the latest developments in HP synchrotron techniques, their applications, and current problems, followed by a discussion of HP scientific studies using x-rays in the key multidisciplinary fields. These HP studies include: HP x-ray emission spectroscopy, which provides information on the filled electronic states of HP samples; HP x-ray Raman spectroscopy, which probes the HP chemical bonding changes of light elements; HP electronic inelastic x-ray scattering spectroscopy, which accesses high energy electronic phenomena, including electronic band structure, Fermi surface, excitons, plasmons, and their dispersions; HP resonant inelastic x-ray scattering spectroscopy, which probes shallow core excitations, multiplet structures, and spin-resolved electronic structure; HP nuclear resonant x-ray spectroscopy, which provides phonon densities of state and time-resolved Mössbauer information; HP x-ray imaging, which provides information on hierarchical structures, dynamic processes, and internal strains; HP x-ray diffraction, which determines the fundamental structures and densities of single-crystal, polycrystalline, nanocrystalline, and non-crystalline materials; and HP radial x-ray diffraction, which yields deviatoric, elastic and rheological information. Integrating these tools with hydrostatic or uniaxial pressure media, laser and resistive heating, and cryogenic cooling, has enabled investigations of the structural, vibrational, electronic, and magnetic properties of materials over a wide range of pressure-temperature conditions.

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Section: Hp Crystallographymentioning

confidence: 99%

High-pressure studies with x-rays using diamond anvil cells

2016

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“…The algorithm identifies crystallographic orientations through finding replicas of the set of theoretical scattering vectors in the measured dataset. A different indexing program, ImageD11, has also recently been applied to a high P DAC data process (15).…”

Section: Determination Of Crystallographic Orientations Of Ppv Crystamentioning

confidence: 99%

Single-crystal structure determination of (Mg,Fe)SiO₃postperovskite

Zhang

Meng

Dera

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

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Knowledge of the structural properties of mantle phases is critical for understanding the enigmatic seismic features observed in the Earth's lower mantle down to the core-mantle boundary. However, our knowledge of lower mantle phase equilibria at high pressure (P) and temperature (T) conditions has been based on limited information provided by powder X-ray diffraction technique and theoretical calculations. Here, we report the in situ single-crystal structure determination of (Mg,Fe)SiO 3 postperovskite (ppv) at high P and after temperature quenching in a diamond anvil cell. Using a newly developed multigrain single-crystal X-ray diffraction analysis technique in a diamond anvil cell, crystallographic orientations of over 100 crystallites were simultaneously determined at high P in a coarse-grained polycrystalline sample containing submicron ppv grains. Conventional single-crystal structural analysis and refinement methods were applied for a few selected ppv crystallites, which demonstrate the feasibility of the in situ study of crystal structures of submicron crystallites in a multiphase polycrystalline sample contained within a high P device. The similarity of structural models for single-crystal Fe-bearing ppv (∼10 mol% Fe) and Fe-free ppv from previous theoretical calculations suggests that the Fe content in the mantle has a negligible effect on the crystal structure of the ppv phase. T he D″ layer, which represents the lowermost several hundred kilometers of the Earth's mantle, plays a critical role in the dynamics and evolution of our planet's mantle and core. Compositional models suggest that the lower mantle consists mainly of (Mg,Fe)SiO 3 in the perovskite (pv) structure with about 10 mol% Fe (1). MgSiO 3 pv transforms to postperovskite (ppv, CaIrO 3 -type) with the space group Cmcm at the high pressure-temperature (P-T) conditions corresponding to the D″ layer (2-4), and the changes associated with the pv-ppv transition may explain several of the intriguing seismic observations of this region (5-7). The in situ determination of the crystal structure of (Mg,Fe)SiO 3 ppv in its stability field will provide key information for understanding the mechanism of the pv-ppv transition and the processes occurring within the D″ layer. Furthermore, compositional changes in (Mg, Fe)SiO 3 may result in subtle changes in the crystal structure of the ppv phase. Recent powder X-ray diffraction (XRD) experiments on ppv with different Fe content suggest that (Mg 0.6 Fe 0.4 )SiO 3 ppv adopts a structure with the Pmcm space group, indicating a structural change in ppv due to . Precise structure analysis for the ppv phase is required to understand subtle effects of pressure and/or composition on its crystal structure.Single-crystal XRD provides the most precise structural information that can be used to uniquely determine the space group and structural model. However, preparation of suitable singlecrystal ppv samples for conventional single-crystal XRD technique has not been possible. The ppv phase crystallizes into a polyc...

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“…A DAC allows an in situ study of PTs under high pressure using advanced diagnostics such as optical, Raman, and X-ray techniques. [1][2][3][4] Pressure-induced PTs are usually studied within a hydrostatic media. In contrast, strain-induced PTs under high pressure are studied without hydrostatic media, by superposing large plastic shear deformations in a rotational DAC.…”

Section: Introductionmentioning

confidence: 99%

Plastic flows and phase transformations in materials under compression in diamond anvil cell: Effect of contact sliding

Feng

Levitas

Zarechnyy

2013

Journal of Applied Physics

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Modeling of coupled plastic flows and strain-induced phase transformations (PTs) under high pressure in a diamond anvil cell is performed with the focus on the effect of the contact sliding between sample and anvils. Finite element software ABAQUS is utilized and a combination of Coulomb friction and plastic friction is considered. Results are obtained for PTs to weaker, equal-strength, and stronger high pressure phases, using different scaling parameters in a strain-controlled kinetic equation, and with various friction coefficients. Compared to the model with cohesion, artificial shear banding near the constant surface is eliminated. Sliding and the reduction in friction coefficient intensify radial plastic flow in the entire sample (excluding a narrow region near the contact surface) and a reduction in thickness. A reduction in the frictioncoefficient to 0.1 intensifies sliding and increases pressure in the central region. Increases in both plastic strain and pressure lead to intensification of strain-induced PT. The effect of self-locking of sliding is revealed. Multiple experimental phenomena are reproduced and interpreted. Thus, plastic flow and PT can be controlled by controlling friction. Modeling of coupled plastic flows and strain-induced phase transformations (PTs) under high pressure in a diamond anvil cell is performed with the focus on the effect of the contact sliding between sample and anvils. Finite element software ABAQUS is utilized and a combination of Coulomb friction and plastic friction is considered. Results are obtained for PTs to weaker, equal-strength, and stronger high pressure phases, using different scaling parameters in a strain-controlled kinetic equation, and with various friction coefficients. Compared to the model with cohesion, artificial shear banding near the constant surface is eliminated. Sliding and the reduction in friction coefficient intensify radial plastic flow in the entire sample (excluding a narrow region near the contact surface) and a reduction in thickness. A reduction in the friction coefficient to 0.1 intensifies sliding and increases pressure in the central region. Increases in both plastic strain and pressure lead to intensification of strain-induced PT. The effect of self-locking of sliding is revealed. Multiple experimental phenomena are reproduced and interpreted. Thus, plastic flow and PT can be controlled by controlling friction. V C 2013 AIP Publishing LLC.

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High resolution three‐dimensional X‐ray diffraction study of dislocations in grains of MgGeO₃ post‐perovskite at 90 GPa

Cited by 47 publications

References 59 publications

High-pressure studies with x-rays using diamond anvil cells

High-pressure studies with x-rays using diamond anvil cells

Single-crystal structure determination of (Mg,Fe)SiO₃postperovskite

Plastic flows and phase transformations in materials under compression in diamond anvil cell: Effect of contact sliding

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High resolution three‐dimensional X‐ray diffraction study of dislocations in grains of MgGeO3 post‐perovskite at 90 GPa

Cited by 47 publications

References 59 publications

High-pressure studies with x-rays using diamond anvil cells

High-pressure studies with x-rays using diamond anvil cells

Single-crystal structure determination of (Mg,Fe)SiO3postperovskite

Plastic flows and phase transformations in materials under compression in diamond anvil cell: Effect of contact sliding

Contact Info

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High resolution three‐dimensional X‐ray diffraction study of dislocations in grains of MgGeO₃ post‐perovskite at 90 GPa

Single-crystal structure determination of (Mg,Fe)SiO₃postperovskite