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arXiv · 2110.00524

Iron-rich Fe-O compounds with closest-packed layers at core pressures

Jin Liu·Yang Sun·Chaojia Lv·Feng Zhang·Suyu Fu·Vitali B. Prakapenka·Cai-Zhuang Wang·Kai-Ming Ho·Jung-Fu Lin·Renata M. Wentzcovitch
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Abstract

Oxygen solubility in solid iron is extremely low, even at high pressures and temperatures. Thus far, no Fe-O compounds between Fe and FeO endmembers have been reported experimentally. We observed chemical reactions of Fe with FeO or Fe$_2$O$_3$ $in\ situ$ x-ray diffraction experiments at 220-260 GPa and 3,000-3,500 K. The refined diffraction patterns are consistent with a series of Fe$_n$O (n $>$ 1) compounds (e.g., Fe$_{25}$O$_{13}$ and Fe$_{28}$O$_{14}$) identified using the adaptive genetic algorithm. Like $\epsilon$-Fe in the hexagonal close-packed (hcp) structure, the structures of Fe$_n$O compounds consist of oxygen-only close-packed monolayers distributed between iron-only layers. $Ab\ initio$ calculations show systematic electronic properties of these compounds that have ramifications for the physical properties of Earth's inner core.

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Jin Liu, Yang Sun, Chaojia Lv, Feng Zhang, Suyu Fu, Vitali B. Prakapenka, Cai-Zhuang Wang, Kai-Ming Ho, Jung-Fu Lin, Renata M. Wentzcovitch. 2021-10-01. Iron-rich Fe-O compounds with closest-packed layers at core pressures. https://arxiv.org/abs/2110.00524

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