Iron-rich Fe-O compounds at Earth's core pressures

ORAL

Abstract

Oxygen is the most abundant element on Earth. While pervasive in the mantle, its presence in the core is still a subject of debate but critical to our understanding of the core-mantle co-evolution and geomagnetic field generation. Thus far, iron monoxide (FeO) is the only known stoichiometric compound in the Fe-FeO system, and the existence of iron-rich Fe-O compounds (FenO with n > 1) has long been questioned. Here we report that iron reacts with FeO and Fe2O3 at 220-260 GPa and 3,000-3,500 K in laser-heated diamond-anvil cells. Using the adaptive genetic algorithm, we find the reaction products consist of a series of FenO stoichiometric compounds and solid solutions (e.g., Fe25O13 and Fe28O14) whose X-ray diffraction patterns agree well with Le Bail refinements of the experimental reaction products. Like ε-Fe, FenO compounds have a typical hexagonal close-packed layered structure, featuring oxygen-only layers between iron layers. Our results suggest that Fe-rich FenO compounds with unique physical properties become stable under Earth's solid inner core conditions.

*This research was supported by NSF EAR-1918126 and EAR-1918134. Experimental part is supported by the NSFC Grants no. 42072052 and U1930401 and EAR-1901808 and EAR-1916941 (J.-F.L.). R.M.W. also acknowledges partial support from the Department of Energy, Theoretical Chemistry Program through grant DE-SC0019759. Computational resources were provided by the Extreme Science and Engineering Discovery Environment (XSEDE) funded by the National Science Foundation through award ACI-1548562. This research also used resources of the Advanced Photon Source (APS), a U.S. Department of Energy (DOE) Office of Science User Facility operated by Argonne National Laboratory under Contract No. DE-AC02-06CH11357. The GeoSoilEnviroCARS at APS is supported by the National Science Foundation - Earth Sciences award EAR-1634415 and the Department of Energy-GeoSciences award DE-FG02-94ER14466

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Publication: https://arxiv.org/abs/2110.00524

Presenters

  • Renata M Wentzcovitch

    • Columbia Univ
    • Columbia University

Authors

  • Renata M Wentzcovitch

    • Columbia Univ
    • Columbia University

  • Yang Sun

    • Columbia University

  • Jin Liu

    • CAS Center for Excellence in Deep Earth Science, Guangzhou, 510640, China, and Center for High Pressure Science and Technology Advanced Research, Beijing 100094, China

  • Vitali B Prakapenka

    • Center for Advanced Radiation Sources, University of Chicago
    • University of Chicago
    • Center for Advanced Radiation Sources, University of Chicago, Chicago, IL 60439, USA
    • GSECARS, Advanced Photon Source, Argonne National Laboratory

  • Feng Zhang

    • Department of Physics, Iowa State University, Ames, Iowa 50011, USA
    • Ames Laboratory

  • Chaojia Lv

    • Center for High Pressure Science and Technology Advanced Research, Beijing 100094, China

  • Suyu Fu

    • Department of Geological Sciences, Jackson School of Geosciences, The University of Texas at Austin, Austin, TX 78712, USA

  • Cai-Zhuang Wang

    • Iowa State University

  • Kai-Ming Ho

    • Ames Laboratory
    • The Ames Laboratory
    • Iowa State University
    • Department of Physics, Iowa State University, Ames, Iowa 50011, USA

  • Jung-Fu Lin

    • University of Texas at Austin
    • Department of Geological Sciences, Jackson School of Geosciences, The University of Texas at Austin, Austin, TX 78712, USA