A density functional theory investigation of the electronic structure and spin moments of magnetite

Noh, Jae Hyung; Osman, Osman I.; Aziz, Saadullah G.; Winget, Paul; Brédas, Jean‐Luc

doi:10.1088/1468-6996/15/4/044202

Cited by 85 publications

(71 citation statements)

References 46 publications

(56 reference statements)

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“…PDOS by standard PBE, based on a plane wave basis set (Figure 3a), agrees well with previous results based on LSDA 25 and PBE, 27 showing that some prominent states of minority Fe Oct 3d electrons cross E F , with a band gap (0.657 eV) in the majority spin-up channel. Note that PBE calculations with and without symmetry give the same PDOS due to the lack of charge disproportionation.…”

Section: Results and Discussionsupporting

confidence: 90%

“…Because of the strong correlation effects among Fe 3d electrons, standard DFT calculations fail to provide an accurate description of Fe 3 O 4 electronic properties and predict magnetic moments for tetrahedral Fe ions (3.34–3.47 μ B 26,27 ) that are much smaller than the experimental value of about 4.2 μ B . 41,42 In contrast, DFT+U calculations, including an additional orbital-dependent interaction for highly localized d orbitals, and hybrid functional calculations, including partial exact exchange, improve the magnetic moment to a value of 4.1 μ B .…”

Section: Introductionmentioning

confidence: 90%

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Band Gap in Magnetite above Verwey Temperature Induced by Symmetry Breaking

Liu

Valentin

2017

J. Phys. Chem. C

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Magnetite exhibits a famous phase transition, called Verwey transition, at the critical temperature TV of about 120 K. Although numerous efforts have been devoted to the understanding of this interesting transition, up to now, it is still under debate whether a charge ordering and a band gap exist in magnetite above TV. Here, we systematically investigate the charge ordering and the electronic properties of magnetite in its cubic phase using different methods based on density functional theory: DFT+U and hybrid functionals. Our results show that, upon releasing the symmetry constraint on the density but not on the geometry, charge disproportionation (Fe2+/Fe3+) is observed, resulting in a band gap of around 0.2 eV at the Fermi level. This implies that the Verwey transition is probably a semiconductor-to-semiconductor transition and that the conductivity mechanism above TV is small polaron hopping.

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Section: Results and Discussionsupporting

confidence: 90%

Section: Introductionmentioning

confidence: 90%

Band Gap in Magnetite above Verwey Temperature Induced by Symmetry Breaking

Liu

Valentin

2017

J. Phys. Chem. C

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“…We performed the analysis for different U values acting on the 3 d orbitals at Fe sites, which directly led us to a way of finding an optimal U value by minimizing the total mean squared deviation between the experimental and calculated formation energies for the considered compounds ( Section 3.3 ). The widely used U Fe value of approximately 4 eV [ 13 , 22 , 23 , 24 , 25 , 26 ] is confirmed, and it provides reasonable band gap predictions for the considered Fe oxides ( Section 3.4 ).…”

Section: Introductionsupporting

confidence: 57%

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

2020

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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.

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“…Here besides the opening of the band gap in spin majority channel, the conductive nature dominated by spin minority FeB 3d-orbital is also well maintained. This important band nature is further confirmed in other theoretical studies [303][304] . 156…”

supporting

confidence: 86%

Extending accurate density functional modeling for the study of interface reactivity and environmental applications

Xu¹

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To my parents, Fangyan and Xingcheniii ACKNOWLEDGEMENTS Seven years in the University of Iowa have become an amazing chapter in my life.I want to express my gratitude to all the people who have helped and encouraged me during this wonderful journey. And among them all, I would like to thank my advisor, Sara E.Mason, for taking a chance to accept me and opening the entire new world of computational chemistry for me. I could never imagine that I can work on so many challenging projects.Your patience, enthusiasm and trust are not just helping me in my academic progress, but also making me grow up through all the ups and downs. I greatly appreciate your guidance and all of the opportunities to reach out in my graduate career.are not just providing the opportunities for us to apply our computational expertise in solving problems in reality, but also letting us understand the structural and chemical complexity of materials under real conditions that pushed our theoretical models to new levels. Our collaborations have built up current and future directions for our projects, and also provided more prospects in bigger academic communities. I am also thankful for the previous members of the Mason group: Dr. Sai Kumar Ramadugu, Dr. Katie Corum, and Dr. Diane Neff, you were extremely helpful for teaching me the knowledge of quantum theory and computational skills, as well as our collaborations in many different projects. iv I would also like to thank our research specialist: Dr. Joseph W. Bennett, for your in-depth understanding of materials and computational chemistry, and your tireless support for the entire group in every aspect. I am not only making academic progress by learning from your knowledge and experience, but also learning how to become a responsible and competent collaborator in team work, and deal with all the obstacles and setbacks during research. I would further like to thank all the group members, Jennifer, Diamond, Irene, Sidney and Blake, for your support and encouragement. It was a great pleasure to work with all of you. Finally, I want to thank my parents, who were thousands miles away, living on the other side of the Pacific Ocean. I just briefly spent about a month with them during my graduate years, but they provided unconditional love and support to me all the time. You constantly believed in me and encouraged my pursuits. I am eternally grateful. v ABSTRACTDensity functional theory (DFT) has become the most widely used first-principles computational method to simulate different atomic, molecular, and solid phase systems based on the electron density assumptions. The complexity of describing a many-body system has been significantly reduced in DFT. However, it also brings in potential error when dealing with a system that involves the interactions between metallic and nonmetallic species. DFT tends to overly-delocalize the electrons in metallic species and sometimes results in the overestimation of reaction energy, metallic properties in insulators, and predicts relative surface stabilities incorre...

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A density functional theory investigation of the electronic structure and spin moments of magnetite

Cited by 85 publications

References 46 publications

Band Gap in Magnetite above Verwey Temperature Induced by Symmetry Breaking

Band Gap in Magnetite above Verwey Temperature Induced by Symmetry Breaking

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

Extending accurate density functional modeling for the study of interface reactivity and environmental applications

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