Published September 25, 2019 | Version v1
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Self-consistent site-dependent DFT+U study of stoichiometric and defective SrMnO3

  • 1. Department of Chemistry and Biochemistry and National Centre for Computational Design and Discovery of Novel Materials (MARVEL), University of Bern, Freiestrasse 3, CH-3012 Bern, Switzerland
  • 2. Theory and Simulation of Materials (THEOS) and National Centre for Computational Design and Discovery of Novel Materials (MARVEL), Ecole Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland

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Description

We propose a self-consistent site-dependent Hubbard U approach for density functional theory (DFT)+U calculations of defects in complex transition metal oxides, using Hubbard parameters computed via linear response theory. The formation of a defect locally perturbs the chemical environment of Hubbard sites in its vicinity, resulting in different Hubbard U parameters for different sites. Using oxygen vacancies in SrMnO3 as a model system, we investigate the dependence of U on the chemical environment and study its influence on the structural, electronic, and magnetic properties of defective bulk and strained thin-film structures. Our results show that a self-consistent U improves the description of stoichiometric bulk SrMnO3 with respect to generalized gradient approximation (GGA) or GGA+U calculations using an empirical U. For defective systems, U changes as a function of the distance of the Hubbard site from the defect, its oxidation state, and the magnetic phase of the bulk structure. Taking into account this dependence, in turn, affects the computed defect formation energies and the predicted strain- and/or defect-induced magnetic phase transitions, especially when occupied localized states appear in the band gap of the material upon defect creation.

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References

Journal reference
C. Ricca, I. Timrov, M. Cococcioni, N. Marzari, U. Aschauer, Physical Review B 99, 094102 (2019), doi: 10.1103/PhysRevB.99.094102