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Determination of Formation Energies and Phase Diagrams of Transition Metal Oxides with DFT+U

1
Fraunhofer Institute for Mechanics of Materials IWM, Wöhlerstraße 11, 79108 Freiburg, Germany
2
Freiburg Materials Research Center (FMF), University of Freiburg, Stefan-Meier- Straße 21, 79104 Freiburg, Germany
*
Author to whom correspondence should be addressed.
Materials 2020, 13(19), 4303; https://doi.org/10.3390/ma13194303
Received: 5 August 2020 / Revised: 15 September 2020 / Accepted: 23 September 2020 / Published: 26 September 2020
Knowledge about the formation energies of compounds is essential to derive phase diagrams of multicomponent phases with respect to elemental reservoirs. The determination of formation energies using common (semi-)local exchange-correlation approximations of the density functional theory (DFT) exhibits well-known systematic errors if applied to oxide compounds containing transition metal elements. In this work, we generalize, reevaluate, and discuss a set of approaches proposed and widely applied in the literature to correct for errors arising from the over-binding of the O2 molecule and from correlation effects of electrons in localized transition-metal orbitals. The DFT+U method is exemplarily applied to iron oxide compounds, and a procedure is presented to obtain the U values, which lead to formation energies and electronic band gaps comparable to the experimental values. Using such corrected formation energies, we derive the phase diagrams for LaFeO3, Li5FeO4, and NaFeO2, which are promising materials for energy conversion and storage devices. A scheme is presented to transform the variables of the phase diagrams from the chemical potentials of elemental phases to those of precursor compounds of a solid-state reaction, which represents the experimental synthesis process more appropriately. The discussed workflow of the methods can directly be applied to other transition metal oxides. View Full-Text
Keywords: transition metal oxides; density functional theory; DFT+U; materials modeling; phase diagrams transition metal oxides; density functional theory; DFT+U; materials modeling; phase diagrams
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MDPI and ACS Style

Mutter, D.; Urban, D.F.; Elsässer, C. Determination of Formation Energies and Phase Diagrams of Transition Metal Oxides with DFT+U. Materials 2020, 13, 4303.

AMA Style

Mutter D, Urban DF, Elsässer C. Determination of Formation Energies and Phase Diagrams of Transition Metal Oxides with DFT+U. Materials. 2020; 13(19):4303.

Chicago/Turabian Style

Mutter, Daniel; Urban, Daniel F.; Elsässer, Christian. 2020. "Determination of Formation Energies and Phase Diagrams of Transition Metal Oxides with DFT+U" Materials 13, no. 19: 4303.

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