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arXiv · 2004.00652

Phase transitions and spin-state of iron in FeO at the conditions of Earth's deep interior

E. Greenberg·R. Nazarov·A. Landa·J. Ying·R. Q. Hood·B. Hen·R. Jeanloz·V. B. Prakapenka·V. V. Struzhkin·G. Kh. Rozenberg·I. Leonov
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Abstract

Iron-bearing oxides undergo a series of pressure-induced electronic, spin and structural transitions that can cause seismic anomalies and dynamic instabilities in Earth's mantle and outer core. We employ x-ray diffraction and x-ray emission spectroscopy along with state-of-the-art density functional plus dynamical mean-field theory (DFT+DMFT) to characterize the electronic structure and spin states, and crystal-structural properties of w\"ustite (Fe$_{1-x}$O) -- a basic oxide component of Earth's interior -- at high pressure-temperature conditions up to 140 GPa and 2100 K. We find that FeO exhibits complex polymorphism under pressure, with abnormal compression behavior associated with electron-spin and crystallographic phase transitions, and resulting in a substantial change of bulk modulus. Our results reveal the existence of a high-pressure phase characterized by a metallic high-spin state of iron at about the pressure-temperature conditions of Earth's core-mantle boundary. The presence of high-spin metallic iron near the base of the mantle can significantly influence the geophysical and geochemical properties of Earth's deep interior.

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E. Greenberg, R. Nazarov, A. Landa, J. Ying, R. Q. Hood, B. Hen, R. Jeanloz, V. B. Prakapenka, V. V. Struzhkin, G. Kh. Rozenberg, I. Leonov. 2020-04-01. Phase transitions and spin-state of iron in FeO at the conditions of Earth's deep interior. https://doi.org/10.1103/physrevb.107.l241103

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