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TT: Fachverband Tiefe Temperaturen

TT 47: Poster Session Correlated Electrons 2

TT 47.13: Poster

Mittwoch, 18. März 2020, 15:00–19:00, P2/3OG

Interplay of electronic structure, magnetic state, and lattice stability in iron oxides under extreme conditions — •Ivan Leonov — M.N. Mikheev Inst. of Metal Physics, Yekaterinburg, Russia — NUST ’MISiS’, Moscow, Russia

The theoretical understanding of iron oxides is of fundamental importance for modeling the properties and evolution of the Earth’s interior. Here, we employ the DFT+DMFT method to determine the electronic structure, magnetic state, and structural phase stability of paramagnetic hematite Fe₂O₃ and pyrite-type FeO₂. Our results reveal a complex interplay between electronic correlations and the lattice in these compounds under extreme conditions. In particular, in the vicinity of a pressure-induced Mott transition Fe₂O₃ exhibits a series of complex electronic, magnetic, and structural transformations, which are accompanied by a site-selective collapse of local magnetic moments and delocalization of the Fe 3d electrons. Our results for structural optimization of FeO₂ within DFT+DMFT show that FeO₂ is a metal and that the oxidation state of Fe is equal to nearly 3+. In contrast to the previous claims, we found no noticeable oxygen-oxygen bonding in FeO₂ to at least 180 GPa (no evidence for the O₂ dimerization), implying that the oxidation state of oxygen in pyrite-type FeO₂ is 1.5- due to the oxygen-to-iron negative charge transfer. Our calculations of the relative phase stability of FeO₂ and Fe₂O₃ reveal that FeO₂ is unstable below ∼40 GPa. In agreement with experiment, it is found to decompose into Fe₂O₃ with release of oxygen, suggesting the importance of iron oxides in oxygen cycling between Earth’s reservoirs.