Iron oxide motifs and structures from 0.1 to 3 TPa

ORAL

Abstract

Iron oxides are fundamental components of planet-forming materials. Understanding the Fe-O system's behavior and properties under pressure can help us identify a plethora of new phases and states possible in exoplanetary interiors, especially terrestrial ones. In this study, we use the adaptive genetic algorithm (AGA) to investigate the structure of iron oxides throughout a wide range of stoichiometries (0.25 < xO < 0.8) and pressures (P = 0.1, 1.0, and 3.0 TPa). At 0.1 TPa, we successfully identify the experimentally known iron oxides phases. However, conventional DFT incorrectly describes the relative energy ordering; it requires self-consistent DFT+U calculations to correct these phases' energetics. At ultra-high pressures, we find some unreported low-enthalpy FexOy phases. Combining the previously predicted structures at 0.35 and 0.5 TPa [Weerasinghe et al., JPCM 27, 455501 (2015)], we show that Fe-O compounds form intricate structural motifs at lower pressures. However, at 1 and 3 TPa, most iron oxides adopt simple BCC or BCT motifs. This finding provides a glimpse of iron coordination and oxidation states in more complex phases with additional elements such as Mg, Si, H, etc. at exoplanetary interior pressures, of which we know very little.

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Presenters

  • Feng Zheng

    • Department of Physics, Xiamen Univ
    • Department of Physics, Xiamen University

Authors

  • Feng Zheng

    • Department of Physics, Xiamen Univ
    • Department of Physics, Xiamen University

  • Yang Sun

    • Iowa State University
    • Department of Applied Physics and Applied Mathematics, Columbia University
    • Columbia Univ

  • Renhai Wang

    • University of Science and Technology of China, Department of Physics
    • Department of Physics, University of Science and Technology of China
    • Iowa State University

  • Yimei Fang

    • Department of Physics, Xiamen Univ
    • Department of Physics, Xiamen University

  • Feng Zhang

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

  • Shunqing Wu

    • Department of Physics, Xiamen Univ
    • Department of Physics, Xiamen University

  • Cai-Zhuang Wang

    • Ames Laboratory, U.S. Department of Energy and Department of Physics and Astronomy, Iowa State University
    • Iowa State University
    • Dept. of Physics and Astronomy, Iowa State University
    • Ames Laboratory and Iowa State University
    • Department of Physics, Iowa State University

  • Renata M Wentzcovitch

    • Columbia Univ
    • Department of Applied Physics and Applied Mathematics, Columbia University
    • Applied Physics and Applied Mathematics, Columbia University
    • Columbia University

  • Kai-Ming Ho

    • Ames Laboratory, U.S. Department of Energy and Department of Physics and Astronomy, Iowa State University
    • Iowa State University/AmesLab
    • Ames Laboratory and Iowa State University
    • Department of Physics, Iowa State University
    • Iowa State University