Unraveling the structure and bonding evolution of the newly discovered iron oxide FeO2

Cheng Lu, Maximilian Amsler, and Changfeng Chen
Phys. Rev. B 98, 054102 – Published 6 August 2018
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Abstract

Recently reported synthesis of FeO2 at high pressure has stimulated great interest in exploring this new iron oxide and elucidating its properties. Here, we present a systematic computational study of crystal structure, chemical bonding, and sound velocity of FeO2 in a wide range of pressure. Our results establish thermodynamic stability of the experimentally observed pyrite phase (P-phase) of FeO2 at pressures above 74 GPa and unveil two metastable FeO2 phases in Pbcn and P42/mnm symmetry at lower pressures. Simulated x-ray diffraction (XRD) spectra of Pbcn and P42/mnmFeO2 match well with measured XRD data of the decompression products of P-phase FeO2, providing compelling evidence for the presence of these metastable phases. Energetic calculations reveal unusually soft O-O bonds in P-phase FeO2 stemming from a low-frequency libration mode of FeO6 octahedra, rendering the O-O bond length highly sensitive to computational and physical environments. Calculated sound-velocity profiles of P-phase FeO2 are markedly different from those of the Pbcn and P42/mnm phases, underscoring their distinct seismic signatures. Our findings offer insights for understanding the rich structural, bonding, and elastic behaviors of this newly discovered iron oxide.

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  • Received 23 May 2018

DOI:https://doi.org/10.1103/PhysRevB.98.054102

©2018 American Physical Society

Physics Subject Headings (PhySH)

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

Cheng Lu1,*, Maximilian Amsler2,†, and Changfeng Chen1,‡

  • 1Department of Physics and High Pressure Science and Engineering Center, University of Nevada, Las Vegas, Nevada 89154, USA
  • 2Laboratory of Atomic and Solid State Physics, Cornell University, Ithaca, New York 14853, USA

  • *cheng.lu@unlv.edu
  • amsler.max@gmail.com
  • chen@physics.unlv.edu

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Issue

Vol. 98, Iss. 5 — 1 August 2018

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