Extreme pressures and temperatures are known to drastically affect the chemistry of iron oxides, resulting in numerous compounds forming homologous seriesnFeOmFe2O3and the appearance of FeO2.Here, based on the results of in situ single-crystal x-ray diffraction, Mössbauer spectroscopy, x-ray absorption spectroscopy, and density-functional theory þ-dynamical mean-field theory calculations, we demonstrate that iron in high-pressure cubic FeO2and isostructural FeO2H0.5is ferric (Fe3þ), and oxygen has a formal valence less than 2. Reduction of oxygen valence from 2, common for oxides, down to 1.5 can be explained by a formation of a localized hole at oxygen sites.
Koemets, E. and Leonov, I. and Bykov, M. and Bykova, E. and Chariton, S. and Aprilis, G. and Fedotenko, T. and Cl’ement, S. and Rouquette, J. and Haines, J. and Cerantola, V. and Glazyrin, K. and McCammon, C. and Prakapenka, V. B. and Hanfland, M. and Liermann, H.-P. and Svitlyk, V. and Torchio, R. and Rosa, A. D. and Irifune, T. and Ponomareva, A. V. and Abrikosov, I. A. and Dubrovinskaia, N. and Dubrovinsky, L., “Revealing the Complex Nature of Bonding in the Binary High-Pressure Compound FeO2”, Phys. Rev. Lett. 126, 106001, DOI: 10.1103/PhysRevLett.126.106001 abstract
