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Efficacy of the DFT + U formalism for modeling hole polarons in perovskite oxides

Erhart, Paul and Klein, Andreas and Åberg, Daniel and Sadigh, Babak :
Efficacy of the DFT + U formalism for modeling hole polarons in perovskite oxides.
[Online-Edition: http://dx.doi.org/10.1103/PhysRevB.90.035204]
In: Physical Review B, 90 (3) 035204. ISSN 1098-0121
[Article] , (2014)
Note:

SFB 595 B7

Official URL: http://dx.doi.org/10.1103/PhysRevB.90.035204

Abstract

We investigate the formation of self-trapped holes (STH) in three prototypical perovskites (SrTiO3, BaTiO3, PbTiO3) using a combination of density functional theory (DFT) calculations with local potentials and hybrid functionals. First we construct a local correction potential for polaronic configurations in SrTiO3 that is applied via the DFT + U method and matches the forces from hybrid calculations. We then use the DFT + U potential to search the configuration space and locate the lowest energy STH configuration. It is demonstrated that both the DFT + U potential and the hybrid functional yield a piecewise linear dependence of the total energy on the occupation of the STH level, suggesting that self-interaction effects have been properly removed. The DFT + U model is found to be transferable to BaTiO3 and PbTiO3, and STH formation energies from DFT + U and hybrid calculations are in close agreement for all three materials. STH formation is found to be energetically favorable in SrTiO3 and BaTiO3 but not in PbTiO3, which can be rationalized by considering the alignment of the valence band edges on an absolute energy scale. In the case of PbTiO3 the strong coupling between Pb 6s and O 2p states lifts the valence band minimum (VBM) compared to SrTiO3 and BaTiO3. This reduces the separation between VBM and STH level and renders the STH configuration metastable with respect to delocalization (band hole state). We expect that the present approach can be adapted to study STH formation also in oxides with different crystal structures and chemical compositions.

Item Type: Article
Erschienen: 2014
Creators: Erhart, Paul and Klein, Andreas and Åberg, Daniel and Sadigh, Babak
Title: Efficacy of the DFT + U formalism for modeling hole polarons in perovskite oxides
Language: English
Abstract:

We investigate the formation of self-trapped holes (STH) in three prototypical perovskites (SrTiO3, BaTiO3, PbTiO3) using a combination of density functional theory (DFT) calculations with local potentials and hybrid functionals. First we construct a local correction potential for polaronic configurations in SrTiO3 that is applied via the DFT + U method and matches the forces from hybrid calculations. We then use the DFT + U potential to search the configuration space and locate the lowest energy STH configuration. It is demonstrated that both the DFT + U potential and the hybrid functional yield a piecewise linear dependence of the total energy on the occupation of the STH level, suggesting that self-interaction effects have been properly removed. The DFT + U model is found to be transferable to BaTiO3 and PbTiO3, and STH formation energies from DFT + U and hybrid calculations are in close agreement for all three materials. STH formation is found to be energetically favorable in SrTiO3 and BaTiO3 but not in PbTiO3, which can be rationalized by considering the alignment of the valence band edges on an absolute energy scale. In the case of PbTiO3 the strong coupling between Pb 6s and O 2p states lifts the valence band minimum (VBM) compared to SrTiO3 and BaTiO3. This reduces the separation between VBM and STH level and renders the STH configuration metastable with respect to delocalization (band hole state). We expect that the present approach can be adapted to study STH formation also in oxides with different crystal structures and chemical compositions.

Journal or Publication Title: Physical Review B
Volume: 90
Number: 3
Publisher: APS Publications
Divisions: 11 Department of Materials and Earth Sciences > Material Science > Surface Science
Zentrale Einrichtungen
DFG-Collaborative Research Centres (incl. Transregio) > Collaborative Research Centres > CRC 595: Electrical fatigue
DFG-Collaborative Research Centres (incl. Transregio) > Collaborative Research Centres > CRC 595: Electrical fatigue > B - Characterisation
DFG-Collaborative Research Centres (incl. Transregio) > Collaborative Research Centres > CRC 595: Electrical fatigue > B - Characterisation > Subproject B7: Polarisation and charging in electrical fatigue ferroelectrics
11 Department of Materials and Earth Sciences > Material Science
11 Department of Materials and Earth Sciences
DFG-Collaborative Research Centres (incl. Transregio) > Collaborative Research Centres
DFG-Collaborative Research Centres (incl. Transregio)
Date Deposited: 15 Dec 2014 09:44
Official URL: http://dx.doi.org/10.1103/PhysRevB.90.035204
Additional Information:

SFB 595 B7

Identification Number: doi:10.1103/PhysRevB.90.035204
Funders: P.E. acknowledges funding from the Area of Advance–Materials Science at Chalmers, the Swedish Research Council in the form of a young researcher grant, and the European Research Council via a Marie Curie career integration grant., A.K. acknowledges support by the German Science Foundation via the collaborative research center on electrical fatigue of functional materials (SFB 595). D.Å. and B.S. acknowledge funding from the NA-22 agency., Parts of this work were prepared at Lawrence Livermore National Laboratory, which is operated by Lawrence Livermore National Security, LLC, for the U.S. DOE-NNSA under Contract No. DE-AC52-07NA27344. , Computer time allocations by the Swedish National Infrastructure for Computing at NSC (Linköping) and C3SE (Gothenburg) are gratefully acknowledged.
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