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  • 1
    Online Resource
    Online Resource
    Dehydrogenation of goethite in Earth’s deep lower mantle
    Proceedings of the National Academy of Sciences ; 2017
    In:  Proceedings of the National Academy of Sciences Vol. 114, No. 7 ( 2017-02-14), p. 1498-1501
    Details
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 114, No. 7 ( 2017-02-14), p. 1498-1501
    Abstract: The cycling of hydrogen influences the structure, composition, and stratification of Earth’s interior. Our recent discovery of pyrite-structured iron peroxide (designated as the P phase) and the formation of the P phase from dehydrogenation of goethite FeO 2 H implies the separation of the oxygen and hydrogen cycles in the deep lower mantle beneath 1,800 km. Here we further characterize the residual hydrogen, x , in the P-phase FeO 2 H x . Using a combination of theoretical simulations and high-pressure–temperature experiments, we calibrated the x dependence of molar volume of the P phase. Within the current range of experimental conditions, we observed a compositional range of P phase of 0.39 〈 x 〈 0.81, corresponding to 19–61% dehydrogenation. Increasing temperature and heating time will help release hydrogen and lower x , suggesting that dehydrogenation could be approaching completion at the high-temperature conditions of the lower mantle over extended geological time. Our observations indicate a fundamental change in the mode of hydrogen release from dehydration in the upper mantle to dehydrogenation in the deep lower mantle, thus differentiating the deep hydrogen and hydrous cycles.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
    URL: Article
    DOI: 10.1073/pnas.1620644114
    RVK:
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    RVK:
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    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 2017
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  • 2
    Online Resource
    Online Resource
    Hydrogen storage in molecular compounds
    Proceedings of the National Academy of Sciences ; 2004
    In:  Proceedings of the National Academy of Sciences Vol. 101, No. 3 ( 2004-01-20), p. 708-710
    Details
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 101, No. 3 ( 2004-01-20), p. 708-710
    Abstract: At low temperature ( T ) and high pressure ( P ), gas molecules can be held in ice cages to form crystalline molecular compounds that may have application for energy storage. We synthesized a hydrogen clathrate hydrate, H 2 (H 2 O) 2 , that holds 50 g/liter hydrogen by volume or 5.3 wt %. The clathrate, synthesized at 200–300 MPa and 240–249 K, can be preserved to ambient P at 77 K. The stored hydrogen is released when the clathrate is warmed to 140 K at ambient P . Low T also stabilizes other molecular compounds containing large amounts of molecular hydrogen, although not to ambient P , e.g., the stability field for H 2 (H 2 O) filled ice (11.2 wt % molecular hydrogen) is extended from 2,300 MPa at 300 K to 600 MPa at 190 K, and that for (H 2 ) 4 CH 4 (33.4 wt % molecular hydrogen) is extended from 5,000 MPa at 300 K to 200 MPa at 77 K. These unique characteristics show the potential of developing low- T molecular crystalline compounds as a new means for hydrogen storage.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
    URL: Article
    DOI: 10.1073/pnas.0307449100
    RVK:
    TA 1000
    RVK:
    WA 15000
    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 2004
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  • 3
    Online Resource
    Online Resource
    Nanoprobe measurements of materials at megabar pressures
    Proceedings of the National Academy of Sciences ; 2010
    In:  Proceedings of the National Academy of Sciences Vol. 107, No. 14 ( 2010-04-06), p. 6140-6145
    Details
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 107, No. 14 ( 2010-04-06), p. 6140-6145
    Abstract: The use of nanoscale x-ray probes overcomes several key limitations in the study of materials up to multimegabar ( 〉  200) pressures, namely, the spatial resolution of measurements of multiple samples, stress gradients, and crystal domains in micron to submicron size samples in diamond-anvil cells. Mixtures of Fe, Pt, and W were studied up to 282 GPa with 250–600 nm size synchrotron x-ray absorption and diffraction probes. The probes readily resolve signals from individual materials, between sample and gasket, and peak pressures, in contrast to the 5-μm-sized x-ray beams that are now becoming routine. The use of nanoscale x-ray beams also enables single-crystal x-ray diffraction studies in nominally polycrystalline samples at ultrahigh pressures, as demonstrated in measurements of (Mg,Fe)SiO 3 postperovskite. These capabilities have potential for driving a push toward higher maximum pressures and further miniaturization of high-pressure devices, in the process advancing studies at extreme conditions.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
    URL: Article
    DOI: 10.1073/pnas.1001141107
    RVK:
    TA 1000
    RVK:
    WA 15000
    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 2010
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  • 4
    Online Resource
    Online Resource
    Substitutional alloy of Ce and Al
    Proceedings of the National Academy of Sciences ; 2009
    In:  Proceedings of the National Academy of Sciences Vol. 106, No. 8 ( 2009-02-24), p. 2515-2518
    Details
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 106, No. 8 ( 2009-02-24), p. 2515-2518
    Abstract: The formation of substitutional alloys has been restricted to elements with similar atomic radii and electronegativity. Using high-pressure at 298 K, we synthesized a face-centered cubic disordered alloy of highly dissimilar elements (large Ce and small Al atoms) by compressing the Ce 3 Al intermetallic compound 〉 15 GPa or the Ce 3 Al metallic glass 〉 25 GPa. Synchrotron X-ray diffraction, Ce L 3 -edge absorption spectroscopy, and ab initio calculations revealed that the pressure-induced Kondo volume collapse and 4 f electron delocalization of Ce reduced the differences between Ce and Al and brought them within the Hume-Rothery (HR) limit for substitutional alloying. The alloy remained after complete release of pressure, which was also accompanied by the transformation of Ce back to its ambient 4 f electron localized state and reversal of the Kondo volume collapse, resulting in a non-HR alloy at ambient conditions.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
    URL: Article
    DOI: 10.1073/pnas.0813328106
    RVK:
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    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 2009
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  • 5
    Online Resource
    Online Resource
    X-rayInduced Dissociation of H 2 O and Formation of an O 2 H 2 Alloy at High Pressure
    American Association for the Advancement of Science (AAAS) ; 2006
    In:  Science Vol. 314, No. 5799 ( 2006-10-27), p. 636-638
    Details
    In: Science, American Association for the Advancement of Science (AAAS), Vol. 314, No. 5799 ( 2006-10-27), p. 636-638
    Abstract: When subjected to high pressure and extensive x-radiation, water (H 2 O) molecules cleaved, forming O–O and H–H bonds. The oxygen (O) and hydrogen (H) framework in ice VII was converted into a molecular alloy of O 2 and H 2 . X-ray diffraction, x-ray Raman scattering, and optical Raman spectroscopy demonstrated that this crystalline solid differs from previously known phases. It remained stable with respect to variations in pressure, temperature, and further x-ray and laser exposure, thus opening new possibilities for studying molecular interactions in the hydrogen-oxygen binary system.
    Type of Medium: Online Resource
    ISSN: 0036-8075 , 1095-9203
    URL: Article
    DOI: 10.1126/science.1132884
    RVK:
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    RVK:
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    Language: English
    Publisher: American Association for the Advancement of Science (AAAS)
    Publication Date: 2006
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  • 6
    Online Resource
    Online Resource
    Bonding Changes in Compressed Superhard Graphite
    American Association for the Advancement of Science (AAAS) ; 2003
    In:  Science Vol. 302, No. 5644 ( 2003-10-17), p. 425-427
    Details
    In: Science, American Association for the Advancement of Science (AAAS), Vol. 302, No. 5644 ( 2003-10-17), p. 425-427
    Abstract: Compressed under ambient temperature, graphite undergoes a transition at ∼17 gigapascals. The near K-edge spectroscopy of carbon using synchrotron x-ray inelastic scattering reveals that half of the π-bonds between graphite layers convert to σ-bonds, whereas the other half remain as π-bonds in the high-pressure form. The x-ray diffraction pattern of the high-pressure form is consistent with a distorted graphite structure in which bridging carbon atoms between graphite layers pair and form σ-bonds, whereas the nonbridging carbon atoms remain unpaired with π-bonds. The high-pressure form is superhard, capable of indenting cubic-diamond single crystals.
    Type of Medium: Online Resource
    ISSN: 0036-8075 , 1095-9203
    URL: Article
    DOI: 10.1126/science.1089713
    RVK:
    TA 1000
    RVK:
    WA 15000
    Language: English
    Publisher: American Association for the Advancement of Science (AAAS)
    Publication Date: 2003
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  • 7
    Online Resource
    Online Resource
    Storage of molecular hydrogen in an ammonia borane compound at high pressure
    Proceedings of the National Academy of Sciences ; 2009
    In:  Proceedings of the National Academy of Sciences Vol. 106, No. 20 ( 2009-05-19), p. 8113-8116
    Details
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 106, No. 20 ( 2009-05-19), p. 8113-8116
    Abstract: We studied ammonia borane (AB), NH 3 BH 3 , in the presence of excess hydrogen (H 2 ) pressure and discovered a solid phase, AB(H 2 ) x , where x ≈1.3–2. The new AB–H 2 compound can store an estimated 8–12 wt % molecular H 2 in addition to the chemically bonded H 2 in AB. This phase formed slowly at 6.2 GPa, but the reaction rate could be enhanced by crushing the AB sample to increase its contact area with H 2 . The compound has 2 Raman H 2 vibron peaks from the absorbed H 2 in this phase: one (ν 1 ) at frequency 70 cm −1 below the free H 2 vibron, and the other (ν 2 ) at higher frequency overlapping with the free H 2 vibron at 6 GPa. The peaks shift linearly over the pressure interval of 6–16 GPa with average pressure coefficients of dν 1 /d P = 4 cm −1 /GPa and dν 2 /d P = 6 cm −1 /GPa. The formation of the compound is accompanied by changes in the N–H and B–H stretching Raman peaks resulting from the AB interactions with H 2 which indicate the structural complexity and low symmetry of this phase. Storage of significant amounts of additional molecular H 2 in AB increases the already high hydrogen content of AB, and may provide guidance for developing improved hydrogen storage materials.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
    URL: Article
    DOI: 10.1073/pnas.0903511106
    RVK:
    TA 1000
    RVK:
    WA 15000
    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 2009
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  • 8
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    Online Resource
    Iron-Rich Post-Perovskite and the Origin of Ultralow-Velocity Zones
    American Association for the Advancement of Science (AAAS) ; 2006
    In:  Science Vol. 312, No. 5773 ( 2006-04-28), p. 564-565
    Details
    In: Science, American Association for the Advancement of Science (AAAS), Vol. 312, No. 5773 ( 2006-04-28), p. 564-565
    Abstract: The boundary layer between the crystalline silicate lower mantle and the liquid iron core contains regions with ultralow seismic velocities. Such low compressional and shear wave velocities and high Poisson's ratio are also observed experimentally in post-perovskite silicate phase containing up to 40 mol% FeSiO 3 endmember. The iron-rich post-perovskite silicate is stable at the pressure-temperature and chemical environment of the core-mantle boundary and can be formed by core-mantle reaction. Mantle dynamics may lead to further accumulation of this material into the ultralow-velocity patches that are observable by seismology.
    Type of Medium: Online Resource
    ISSN: 0036-8075 , 1095-9203
    URL: Article
    DOI: 10.1126/science.1123442
    RVK:
    TA 1000
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    WA 15000
    Language: English
    Publisher: American Association for the Advancement of Science (AAAS)
    Publication Date: 2006
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  • 9
    Online Resource
    Online Resource
    Hydrogen Clusters in Clathrate Hydrate
    American Association for the Advancement of Science (AAAS) ; 2002
    In:  Science Vol. 297, No. 5590 ( 2002-09-27), p. 2247-2249
    Details
    In: Science, American Association for the Advancement of Science (AAAS), Vol. 297, No. 5590 ( 2002-09-27), p. 2247-2249
    Abstract: High-pressure Raman, infrared, x-ray, and neutron studies show that H 2 and H 2 O mixtures crystallize into the sII clathrate structure with an approximate H 2 /H 2 O molar ratio of 1:2. The clathrate cages are multiply occupied, with a cluster of two H 2 molecules in the small cage and four in the large cage. Substantial softening and splitting of hydrogen vibrons indicate increased intermolecular interactions. The quenched clathrate is stable up to 145 kelvin at ambient pressure. Retention of hydrogen at such high temperatures could help its condensation in planetary nebulae and may play a key role in the evolution of icy bodies.
    Type of Medium: Online Resource
    ISSN: 0036-8075 , 1095-9203
    URL: Article
    DOI: 10.1126/science.1075394
    RVK:
    TA 1000
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    WA 15000
    Language: English
    Publisher: American Association for the Advancement of Science (AAAS)
    Publication Date: 2002
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  • 10
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    Online Resource
    Preservation of high-pressure volatiles in nanostructured diamond capsules
    Springer Science and Business Media LLC ; 2022
    In:  Nature Vol. 608, No. 7923 ( 2022-08-18), p. 513-517
    Details
    In: Nature, Springer Science and Business Media LLC, Vol. 608, No. 7923 ( 2022-08-18), p. 513-517
    Type of Medium: Online Resource
    ISSN: 0028-0836 , 1476-4687
    URL: Article
    DOI: 10.1038/s41586-022-04955-z
    RVK:
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    RVK:
    UA 1000
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    Language: English
    Publisher: Springer Science and Business Media LLC
    Publication Date: 2022
    detail.hit.zdb_id: 120714-3
    detail.hit.zdb_id: 1413423-8
    SSG: 11
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