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MM: Fachverband Metall- und Materialphysik

MM 3: Topical Session: Sustainable metallurgy

MM 3.5: Talk

Monday, March 18, 2024, 11:45–12:00, C 130

Artificial negative pressure in DFT+U calculations for iron oxides — •Hao Chen, Christoph Freysoldt, Mira Todorova, and Jörg Neugebauer — Max-Planck-Institut für Eisenforschung GmbH, Düsseldorf, Germany

Off-stoichiometric iron oxides play a crucial role in the process of iron ore reduction. The thermal stability and transformation kinetics of relevant iron oxides depend sensitively on magnetic, configurational, and vibrational degrees of freedom and their interplay, but our understanding in this regard is still limited. In addressing this issue, it's imperative to first achieve a precise and reliable description of the iron oxides, in particular their electronic properties and stability. We employ DFT+U, which is an efficient tool for studying strongly correlated systems, to investigate the stability of Hematite (Fe2O3), Magnetite (Fe3O4), and Wüstite (FeO). We find that the Hubbard U parameter and details of how the projection onto the correlated subspace is implemented may modify even basic materials parameters such as the equilibrium volume by several percent, indicating that the actual ad-hoc choices influence the prediction of lattice constants and bond lengths. We analyze in detail the factors that may contribute to and influence this phenomenon, and explore possible solutions to mitigate the dependence of volume on U.