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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:
    TA 1000
    RVK:
    WA 15000
    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 2017
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  • 2
    Online Resource
    Online Resource
    Highly tunable properties in pressure-treated two-dimensional Dion–Jacobson perovskites
    Proceedings of the National Academy of Sciences ; 2020
    In:  Proceedings of the National Academy of Sciences Vol. 117, No. 28 ( 2020-07-14), p. 16121-16126
    Details
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 117, No. 28 ( 2020-07-14), p. 16121-16126
    Abstract: The application of pressure can achieve novel structures and exotic phenomena in condensed matters. However, such pressure-induced transformations are generally reversible and useless for engineering materials for ambient-environment applications. Here, we report comprehensive high-pressure investigations on a series of Dion–Jacobson (D-J) perovskites A′A n −1 Pb n I 3 n +1 [A′ = 3-(aminomethyl) piperidinium (3AMP), A = methylammonium (MA), n = 1, 2, 4]. Our study demonstrates their irreversible behavior, which suggests pressure/strain engineering could viably improve light-absorber material not only in situ but also ex situ, thus potentially fostering the development of optoelectronic and electroluminescent materials. We discovered that the photoluminescence (PL) intensities are remarkably enhanced by one order of magnitude at mild pressures. Also, higher pressure significantly changes the lattices, boundary conditions of electronic wave functions, and possibly leads to semiconductor–metal transitions. For (3AMP)(MA) 3 Pb 4 I 13 , permanent recrystallization from 2D to three-dimensional (3D) structure occurs upon decompression, with dramatic changes in optical properties.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
    URL: Article
    DOI: 10.1073/pnas.2003561117
    RVK:
    TA 1000
    RVK:
    WA 15000
    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 2020
    detail.hit.zdb_id: 209104-5
    detail.hit.zdb_id: 1461794-8
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  • 3
    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
    detail.hit.zdb_id: 209104-5
    detail.hit.zdb_id: 1461794-8
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  • 4
    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
    detail.hit.zdb_id: 209104-5
    detail.hit.zdb_id: 1461794-8
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  • 5
    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:
    TA 1000
    RVK:
    WA 15000
    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 2009
    detail.hit.zdb_id: 209104-5
    detail.hit.zdb_id: 1461794-8
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  • 6
    Online Resource
    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
    RVK:
    WA 15000
    Language: English
    Publisher: American Association for the Advancement of Science (AAAS)
    Publication Date: 2006
    detail.hit.zdb_id: 128410-1
    detail.hit.zdb_id: 2066996-3
    detail.hit.zdb_id: 2060783-0
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  • 7
    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:
    TA 1000
    RVK:
    WA 15000
    Language: English
    Publisher: American Association for the Advancement of Science (AAAS)
    Publication Date: 2006
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    detail.hit.zdb_id: 2066996-3
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    SSG: 11
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  • 8
    Online Resource
    Online Resource
    Sound velocities of Fe and Fe-Si alloy in the Earth’s core
    Proceedings of the National Academy of Sciences ; 2012
    In:  Proceedings of the National Academy of Sciences Vol. 109, No. 26 ( 2012-06-26), p. 10239-10244
    Details
    In: Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 109, No. 26 ( 2012-06-26), p. 10239-10244
    Abstract: Compressional wave velocity-density ( V P  -  ρ ) relations of candidate Fe alloys at relevant pressure-temperature conditions of the Earth’s core are critically needed to evaluate the composition, seismic signatures, and geodynamics of the planet’s remotest region. Specifically, comparison between seismic V P  -  ρ profiles of the core and candidate Fe alloys provides first-order information on the amount and type of potential light elements—including H, C, O, Si, and/or S—needed to compensate the density deficit of the core. To address this issue, here we have surveyed and analyzed the literature results in conjunction with newly measured V P  -  ρ results of hexagonal closest-packed (hcp) Fe and hcp-Fe 0.85 Si 0.15 alloy using in situ high-energy resolution inelastic X-ray scattering and X-ray diffraction. The nature of the Fe-Si alloy where Si is readily soluble in Fe represents an ideal solid-solution case to better understand the light-element alloying effects. Our results show that high temperature significantly decreases the V P of hcp-Fe at high pressures, and the Fe-Si alloy exhibits similar high-pressure V P  -  ρ behavior to hcp-Fe via a constant density offset. These V P  -  ρ data at a given temperature can be better described by an empirical power-law function with a concave behavior at higher densities than with a linear approximation. Our new datasets, together with literature results, allow us to build new V P  -  ρ models of Fe alloys in order to determine the chemical composition of the core. Our models show that the V P  -  ρ profile of Fe with 8 wt % Si at 6,000 K matches well with the Preliminary Reference Earth Model of the inner core.
    Type of Medium: Online Resource
    ISSN: 0027-8424 , 1091-6490
    URL: Article
    DOI: 10.1073/pnas.1207086109
    RVK:
    TA 1000
    RVK:
    WA 15000
    Language: English
    Publisher: Proceedings of the National Academy of Sciences
    Publication Date: 2012
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  • 9
    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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    detail.hit.zdb_id: 1461794-8
    SSG: 11
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  • 10
    Online Resource
    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:
    TA 1000
    RVK:
    UA 1000
    RVK:
    WA 15000
    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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