Published June 22, 2020 | Version v1
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Electronic structure of pristine and Ni-substituted LaFeO₃ from near edge x-ray absorption fine structure experiments and first-principles simulations

  • 1. Theory and Simulation of Materials (THEOS), and National Centre for Computational Design and Discovery of Novel Materials (MARVEL), École Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland
  • 2. nanotech@surfaces Laboratory and National Centre for Computational Design and Discovery of Novel Materials (MARVEL), Empa - Swiss Federal Laboratories for Materials Science and Technology, CH-8600 Dübendorf, Switzerland
  • 3. Electron Microscopy Center, Empa - Swiss Federal Laboratories for Materials Science and Technology, CH-8600 Dübendorf, Switzerland
  • 4. nanotech@surfaces Laboratory, Empa - Swiss Federal Laboratories for Materials Science and Technology, CH-8600 Dübendorf, Switzerland
  • 5. State Key Laboratory of Metastable Material Science and Technology, Yanshan University, CN-066004 Qinhuangdao, China
  • 6. High Performance Ceramics Laboratory, Empa - Swiss Federal Laboratories for Materials Science and Technology, CH-8600 Dübendorf, Switzerland
  • 7. Department for Materials, Nonmetallic Inorganic Materials, ETH Zurich, Swiss Federal Institute of Technology, CH-8037 Zurich, Switzerland
  • 8. Vocational School of Technical Sciences, Department of Medical Services and Techniques, Program of Opticianry, Mersin University, TR-33343 Yenisehir, Mersin, Turkey
  • 9. Advanced Technology Education Research and Application Center, Mersin University, TR-33343 Yenisehir, Mersin, Turkey
  • 10. Department of Physics, University of Pavia, via Bassi 6, I-27100 Pavia, Italy
  • 11. Dipartmento di Fisica, Università di Trento, via Sommarive 14, 38123 Povo, Italy
  • 12. Sorbonne Université, CNRS, Institut des Nanosciences de Paris, UMR7588, F-75252 Paris, France

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Description

We present a joint theoretical and experimental study of the oxygen K-edge spectra for LaFeO₃ and homovalent Ni-substituted LaFeO₃ (LaFe₀.₇₅Ni₀.₂₅O₃), using first-principles simulations based on density-functional theory with extended Hubbard functionals and x-ray absorption near edge structure (XANES) measurements. Ground-state and excited-state XANES calculations employ Hubbard on-site U and inter-site V parameters determined from first principles and the Lanczos recursive method to obtain absorption cross sections, which allows for a reliable description of XANES spectra in transition-metal compounds in a very broad energy range, with an accuracy comparable to that of hybrid functionals but at a substantially lower cost. We show that standard gradient-corrected exchange-correlation functionals fail in capturing accurately the electronic properties of both materials. In particular, for LaFe₀.₇₅Ni₀.₂₅O₃ they do not reproduce its semiconducting behaviour and provide a poor description of the pre-edge features at the O K edge. The inclusion of Hubbard interactions leads to a drastic improvement, accounting for the semiconducting ground state of LaFe₀.₇₅Ni₀.₂₅O₃ and for good agreement between calculated and measured XANES spectra. We show that the partial substitution of Ni for Fe affects the conduction-band bottom by generating a strongly hybridized O(2p)-Ni(3d) minority-spin empty electronic state. The present work, based on a consistent correction of self-interaction errors, outlines the crucial role of extended Hubbard functionals to describe the electronic structure of complex transition-metal oxides such as LaFeO₃ and LaFe₀.₇₅Ni₀.₂₅O₃ and paves the way to future studies on similar systems.

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References

Journal reference (Paper which outlines the crucial role of extended Hubbard functionals to describe the electronic structure of complex transition-metal oxides such as pristine and Ni-substituted LaFeO3 and paves the way to future studies on similar systems)
I. Timrov, P. Agrawal, X. Zhang, S. Erat, R. Liu, A. Braun, M. Cococcioni, M. Calandra, N. Marzari, D. Passerone, Phys. Rev. Research 2, 033265 (2020), doi: 10.1103/PhysRevResearch.2.033265

Preprint (Preprint of the paper)
I. Timrov, P. Agrawal, X. Zhang, S. Erat, R. Liu, A. Braun, M. Cococcioni, M. Calandra, N. Marzari, D. Passerone, arXiv:2004.04142 (2020)