Importance of the Hubbard U parameter to explore accurate electronic and optical behaviour of BiFeO₃

Abstract

Based upon Hubbard U corrected density functional theory (DFT), electronic and optical responses of multiferroic Bismuth ferrite (BiFeO3, BFO) have been critically explored. Treating BFO as a strongly correlated insulating system, a Hubbard U parameter is considered for accurate description of localized Fe-3d states. However, U parameter for Fe-3d state is not sufficient as 2p states of O atoms are greatly influenced by Fe-3d states. Similar U parameters for Fe-3d as well as O-2p states are considered. Effective U value around 4.3 eV not only solves the bandgap mismatch of BFO from both theoretical and experimental aspects but also predicts the exact nature of the bandgap. Moreover, within this framework, optical responses of BFO are critically investigated. Multiple transitions appearing in both theoretical and experimental absorption spectra have been well explained by crystal field transitions of Fe3+ ions in d5 high spin state, supported by the density of states (DOS) curve of BFO. Therefore based upon DFT+U approach, accurate electronic and optical characteristics of BFO are critically explored which is essential for its multidirectional application perspectives.

Influence of near-surface oxide layers on TiFe hydrogenation: mechanistic insights and implications for hydrogen storage applications

“…All calculations were spin-polarized and a DFT-D3 dispersion correction scheme was used. 41 Based on Dudarev's implementation of the Hubbard model for a system of interacting electrons, 42 an effective on-site Coulomb interaction parameter (U eff ) of 4.0 and 4.3 eV was applied to Ti 43,44 and Fe, 45,46 respectively (except for the reaction energy barrier calculations, see below). The charge states on the oxide layers were assessed with a density-derived electrostatic and chemical method (DDEC6) as implemented in the chargemol program.…”

Magnetic and thermoelectric properties of REMoN3 (RE = La, Ce, Pr, Nd, and Sm): A first‐principles study

“…In systems with localized electrons, such as transition metal oxides and rare‐earth compounds, DFT often fails to capture the energy levels and electronic distribution correctly due to the presence of correlated electron interaction. To correctly explore the electronic structure, we introduced DFT + U to treat the strongly correlated d and f ‐states of Mo and rare‐earth ( RE = La, Ce, Pr, Nd, Sm) elements, respectively [25]. Furthermore, in the current study, total magnetic moments (μ tot ) were calculated, and the materials revealed ferromagnetic properties, except for CeMoN 3 , which exhibited an antiferromagnetic character.…”

“…In systems with localized electrons, such as transition metal oxides and rare-earth compounds, DFT often fails to capture the energy levels and electronic distribution correctly due to the presence of correlated electron interaction. To correctly explore the electronic structure, we introduced DFT + U to treat the strongly correlated d and f-states of Mo and rare-earth (RE = La, Ce, Pr, Nd, Sm) elements, respectively [25].…”

Understanding and optimizing the sensitization of anatase titanium dioxide surface with hematite clusters

“…2 because of the localized d electrons. This is a well-known issue in predicting the electronic structure of transition metals oxides[61][62][63][64][65]. Previously, for instance, Labat et al[66], Mattioli et al[62] and Di Valentin et al[67] have reported the band gaps of 2.08…”