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  • 1
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    Body-centered cubic iron-nickel alloy in Earth's core (2007)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2007-06-30
    Description: Cosmochemical, geochemical, and geophysical studies provide evidence that Earth's core contains iron with substantial (5 to 15%) amounts of nickel. The iron-nickel alloy Fe(0.9)Ni(0.1) has been studied in situ by means of angle-dispersive x-ray diffraction in internally heated diamond anvil cells (DACs), and its resistance has been measured as a function of pressure and temperature. At pressures above 225 gigapascals and temperatures over 3400 kelvin, Fe(0.9)Ni(0.1) adopts a body-centered cubic structure. Our experimental and theoretical results not only support the interpretation of shockwave data on pure iron as showing a solid-solid phase transition above about 200 gigapascals, but also suggest that iron alloys with geochemically reasonable compositions (that is, with substantial nickel, sulfur, or silicon content) adopt the bcc structure in Earth's inner core.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Dubrovinsky, L -- Dubrovinskaia, N -- Narygina, O -- Kantor, I -- Kuznetzov, A -- Prakapenka, V B -- Vitos, L -- Johansson, B -- Mikhaylushkin, A S -- Simak, S I -- Abrikosov, I A -- New York, N.Y. -- Science. 2007 Jun 29;316(5833):1880-3.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Bayerisches Geoinstitut, Universitat Bayreuth, D-95440 Bayreuth, Germany.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/17600212" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 2
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    Unexpected stable stoichiometries of sodium chlorides (2013)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2013-12-21
    Description: Sodium chloride (NaCl), or rocksalt, is well characterized at ambient pressure. As a result of the large electronegativity difference between Na and Cl atoms, it has highly ionic chemical bonding (with 1:1 stoichiometry dictated by charge balance) and B1-type crystal structure. By combining theoretical predictions and diamond anvil cell experiments, we found that new materials with different stoichiometries emerge at high pressures. Compounds such as Na3Cl, Na2Cl, Na3Cl2, NaCl3, and NaCl7 are theoretically stable and have unusual bonding and electronic properties. To test this prediction, we synthesized cubic and orthorhombic NaCl3 and two-dimensional metallic tetragonal Na3Cl. These experiments establish that compounds violating chemical intuition can be thermodynamically stable even in simple systems at nonambient conditions.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Zhang, Weiwei -- Oganov, Artem R -- Goncharov, Alexander F -- Zhu, Qiang -- Boulfelfel, Salah Eddine -- Lyakhov, Andriy O -- Stavrou, Elissaios -- Somayazulu, Maddury -- Prakapenka, Vitali B -- Konopkova, Zuzana -- New York, N.Y. -- Science. 2013 Dec 20;342(6165):1502-5. doi: 10.1126/science.1244989.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Applied Physics, China Agricultural University, Beijing 100080, China.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/24357316" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 3
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    Mineralogy. Discovery of bridgmanite, the most abundant mineral in Earth, in a shocked meteorite (2014)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2014-11-29
    Description: Meteorites exposed to high pressures and temperatures during impact-induced shock often contain minerals whose occurrence and stability normally confine them to the deeper portions of Earth's mantle. One exception has been MgSiO3 in the perovskite structure, which is the most abundant solid phase in Earth. Here we report the discovery of this important phase as a mineral in the Tenham L6 chondrite and approved by the International Mineralogical Association (specimen IMA 2014-017). MgSiO3-perovskite is now called bridgmanite. The associated phase assemblage constrains peak shock conditions to ~ 24 gigapascals and 2300 kelvin. The discovery concludes a half century of efforts to find, identify, and characterize a natural specimen of this important mineral.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Tschauner, Oliver -- Ma, Chi -- Beckett, John R -- Prescher, Clemens -- Prakapenka, Vitali B -- Rossman, George R -- New York, N.Y. -- Science. 2014 Nov 28;346(6213):1100-2. doi: 10.1126/science.1259369.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Geoscience and High Pressure Science and Engineering Center, University of Nevada, Las Vegas, NV 89134, USA. olivert@physics.unlv.edu. ; Division of Geology and Planetary Science, California Institute of Technology, Pasadena, CA 91125, USA. ; Center of Advanced Radiation Sources, University of Chicago, Chicago, IL 60632, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/25430766" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 4
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    Iron-rich post-perovskite and the origin of ultralow-velocity zones (2006)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2006-04-29
    Description: 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% FeSiO3 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.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Mao, Wendy L -- Mao, Ho-Kwang -- Sturhahn, Wolfgang -- Zhao, Jiyong -- Prakapenka, Vitali B -- Meng, Yue -- Shu, Jinfu -- Fei, Yingwei -- Hemley, Russell J -- New York, N.Y. -- Science. 2006 Apr 28;312(5773):564-5.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Lujan Neutron Scattering Center, Los Alamos National Laboratory, Los Alamos, NM 87545, USA. wmao@lanl.gov〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/16645091" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 5
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    Spin transition zone in Earth's lower mantle (2007)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2007-09-22
    Description: Mineral properties in Earth's lower mantle are affected by iron electronic states, but representative pressures and temperatures have not yet been probed. Spin states of iron in lower-mantle ferropericlase have been measured up to 95 gigapascals and 2000 kelvin with x-ray emission in a laser-heated diamond cell. A gradual spin transition of iron occurs over a pressure-temperature range extending from about 1000 kilometers in depth and 1900 kelvin to 2200 kilometers and 2300 kelvin in the lower mantle. Because low-spin ferropericlase exhibits higher density and faster sound velocities relative to the high-spin ferropericlase, the observed increase in low-spin (Mg,Fe)O at mid-lower mantle conditions would manifest seismically as a lower-mantle spin transition zone characterized by a steeper-than-normal density gradient.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Lin, Jung-Fu -- Vanko, Gyorgy -- Jacobsen, Steven D -- Iota, Valentin -- Struzhkin, Viktor V -- Prakapenka, Vitali B -- Kuznetsov, Alexei -- Yoo, Choong-Shik -- New York, N.Y. -- Science. 2007 Sep 21;317(5845):1740-3.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Lawrence Livermore National Laboratory (LLNL), 7000 East Avenue, Livermore, CA 94550, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/17885134" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 6
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    Terapascal static pressure generation with ultrahigh yield strength nanodiamond (2016)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2016-07-22
    Description: Studies of materials’ properties at high and ultrahigh pressures lead to discoveries of unique physical and chemical phenomena and a deeper understanding of matter. In high-pressure research, an achievable static pressure limit is imposed by the strength of available strong materials and design of high-pressure devices. Using a high-pressure and high-temperature technique, we synthesized optically transparent microballs of bulk nanocrystalline diamond, which were found to have an exceptional yield strength (~460 GPa at a confining pressure of ~70 GPa) due to the unique microstructure of bulk nanocrystalline diamond. We used the nanodiamond balls in a double-stage diamond anvil cell high-pressure device that allowed us to generate static pressures beyond 1 TPa, as demonstrated by synchrotron x-ray diffraction. Outstanding mechanical properties (strain-dependent elasticity, very high hardness, and unprecedented yield strength) make the nanodiamond balls a unique device for ultrahigh static pressure generation. Structurally isotropic, homogeneous, and made of a low-Z material, they are promising in the field of x-ray optical applications.
    Electronic ISSN: 2375-2548
    Topics: Natural Sciences in General
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  • 7
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    Uranium polyhydrides at moderate pressures: Prediction, synthesis, and expected superconductivity (2018)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2018
    Description: 〈p〉Hydrogen-rich hydrides attract great attention due to recent theoretical (〈cross-ref type="bib" refid="R1"〉〈i〉1〈/i〉〈/cross-ref〉) and then experimental discovery of record high-temperature superconductivity in H〈sub〉3〈/sub〉S [〈i〉T〈/i〉〈sub〉c〈/sub〉 = 203 K at 155 GPa (〈cross-ref type="bib" refid="R2"〉〈i〉2〈/i〉〈/cross-ref〉)]. Here we search for stable uranium hydrides at pressures up to 500 GPa using ab initio evolutionary crystal structure prediction. Chemistry of the U-H system turned out to be extremely rich, with 14 new compounds, including hydrogen-rich UH〈sub〉5〈/sub〉, UH〈sub〉6〈/sub〉, U〈sub〉2〈/sub〉H〈sub〉13〈/sub〉, UH〈sub〉7〈/sub〉, UH〈sub〉8〈/sub〉, U〈sub〉2〈/sub〉H〈sub〉17〈/sub〉, and UH〈sub〉9〈/sub〉. Their crystal structures are based on either common face-centered cubic or hexagonal close-packed uranium sublattice and unusual H〈sub〉8〈/sub〉 cubic clusters. Our high-pressure experiments at 1 to 103 GPa confirm the predicted UH〈sub〉7〈/sub〉, UH〈sub〉8〈/sub〉, and three different phases of UH〈sub〉5〈/sub〉, raising confidence about predictions of the other phases. Many of the newly predicted phases are expected to be high-temperature superconductors. The highest-〈i〉T〈/i〉〈sub〉c〈/sub〉 superconductor is UH〈sub〉7〈/sub〉, predicted to be thermodynamically stable at pressures above 22 GPa (with 〈i〉T〈/i〉〈sub〉c〈/sub〉 = 44 to 54 K), and this phase remains dynamically stable upon decompression to zero pressure (where it has 〈i〉T〈/i〉〈sub〉c〈/sub〉 = 57 to 66 K).〈/p〉
    Electronic ISSN: 2375-2548
    Topics: Natural Sciences in General
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  • 8
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    Uranium polyhydrides at moderate pressures: Prediction, synthesis, and expected superconductivity (2018)
    American Association for the Advancement of Science (AAAS)
    Details
    Publication Date: 2018-10-13
    Description: Hydrogen-rich hydrides attract great attention due to recent theoretical ( 1 ) and then experimental discovery of record high-temperature superconductivity in H 3 S [ T c = 203 K at 155 GPa ( 2 )]. Here we search for stable uranium hydrides at pressures up to 500 GPa using ab initio evolutionary crystal structure prediction. Chemistry of the U-H system turned out to be extremely rich, with 14 new compounds, including hydrogen-rich UH 5 , UH 6 , U 2 H 13 , UH 7 , UH 8 , U 2 H 17 , and UH 9 . Their crystal structures are based on either common face-centered cubic or hexagonal close-packed uranium sublattice and unusual H 8 cubic clusters. Our high-pressure experiments at 1 to 103 GPa confirm the predicted UH 7 , UH 8 , and three different phases of UH 5 , raising confidence about predictions of the other phases. Many of the newly predicted phases are expected to be high-temperature superconductors. The highest- T c superconductor is UH 7 , predicted to be thermodynamically stable at pressures above 22 GPa (with T c = 44 to 54 K), and this phase remains dynamically stable upon decompression to zero pressure (where it has T c = 57 to 66 K).
    Electronic ISSN: 2375-2548
    Topics: Natural Sciences in General
    Published by American Association for the Advancement of Science (AAAS)
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  • 9
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    Ice-VII inclusions in diamonds: Evidence for aqueous fluid in Earths deep mantle (2018)
    American Association for the Advancement of Science (AAAS)
    In: Science
    Details
    Publication Date: 2018-03-09
    Description: Water-rich regions in Earth’s deeper mantle are suspected to play a key role in the global water budget and the mobility of heat-generating elements. We show that ice-VII occurs as inclusions in natural diamond and serves as an indicator for such water-rich regions. Ice-VII, the residue of aqueous fluid present during growth of diamond, crystallizes upon ascent of the host diamonds but remains at pressures as high as 24 gigapascals; it is now recognized as a mineral by the International Mineralogical Association. In particular, ice-VII in diamonds points toward fluid-rich locations in the upper transition zone and around the 660-kilometer boundary.
    Keywords: Geochemistry, Geophysics
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Geosciences , Computer Science , Medicine , Natural Sciences in General , Physics
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