Properties of oxygen vacancy and hydrogen interstitial defects in strontium titanate: DFT + Ud,p calculations
Properties of oxygen vacancy and hydrogen interstitial defects in strontium titanate: DFT + Ud,p calculations
This work presents extensive theoretical studies focused on the mixed ion-electron transport in cubic strontium titanate (STO). A new approach to the description of this difficult system was developed within the framework of linear-scaling Kohn-Sham density functional theory, as realized in the ONETEP program. The description we present is free of any empirical parameters and relies on the Hubbard U and Hund's J corrections applied to both Ti and O atoms. The proposed methodology was validated by considering perfect STO. Its calculated properties were found to be in close agreement with experiments and calculations at higher levels of theory. The validated approach was subsequently employed to study the oxygen vacancy (VO) and the hydrogen interstitial (IH), using very large supercells (625 ± 1 atoms). The relaxed configurations of defects were obtained through fastidious energy minimization and later analyzed from a number of perspectives. The calculated defect formation energies and charge transition levels (CTLs) were found to be in close agreement with the experiment. With the exception of the charge-neutral VO, all considered defects were found to introduce shallow states, located down to 0.2 eV below the conduction band. Our calculations revealed a large 1 eV difference in the thermodynamic and optical CTLs of the neutral VO, explaining the inconsistencies observed-till now-between conduction and spectroscopic measurements. The influence of defects on the bonding characteristics and the crystalline structure of STO was quantified, revealing that both VOand IHdefects lead to a significant polarization and strong tilting of the TiO6octahedra.
18439-18465
Winczewski, Szymon
4c989463-5a91-42fa-99d8-e2aa2faddd46
Dziedzic, Jacek
8e2fdb55-dade-4ae4-bf1f-a148a89e4383
Miruszewski, Tadeusz
716ab41a-1e0b-439a-b46a-2e42bdcaf6b3
Rybicki, Jarosław
07e37045-a3a7-4b76-b2b7-61118a3b92e2
Gazda, Maria
f922f5d6-2bef-4c4b-9949-39845c66aefa
3 November 2022
Winczewski, Szymon
4c989463-5a91-42fa-99d8-e2aa2faddd46
Dziedzic, Jacek
8e2fdb55-dade-4ae4-bf1f-a148a89e4383
Miruszewski, Tadeusz
716ab41a-1e0b-439a-b46a-2e42bdcaf6b3
Rybicki, Jarosław
07e37045-a3a7-4b76-b2b7-61118a3b92e2
Gazda, Maria
f922f5d6-2bef-4c4b-9949-39845c66aefa
Winczewski, Szymon, Dziedzic, Jacek, Miruszewski, Tadeusz, Rybicki, Jarosław and Gazda, Maria
(2022)
Properties of oxygen vacancy and hydrogen interstitial defects in strontium titanate: DFT + Ud,p calculations.
Journal of Physical Chemistry C, 126 (43), .
(doi:10.1021/acs.jpcc.2c04681).
Abstract
This work presents extensive theoretical studies focused on the mixed ion-electron transport in cubic strontium titanate (STO). A new approach to the description of this difficult system was developed within the framework of linear-scaling Kohn-Sham density functional theory, as realized in the ONETEP program. The description we present is free of any empirical parameters and relies on the Hubbard U and Hund's J corrections applied to both Ti and O atoms. The proposed methodology was validated by considering perfect STO. Its calculated properties were found to be in close agreement with experiments and calculations at higher levels of theory. The validated approach was subsequently employed to study the oxygen vacancy (VO) and the hydrogen interstitial (IH), using very large supercells (625 ± 1 atoms). The relaxed configurations of defects were obtained through fastidious energy minimization and later analyzed from a number of perspectives. The calculated defect formation energies and charge transition levels (CTLs) were found to be in close agreement with the experiment. With the exception of the charge-neutral VO, all considered defects were found to introduce shallow states, located down to 0.2 eV below the conduction band. Our calculations revealed a large 1 eV difference in the thermodynamic and optical CTLs of the neutral VO, explaining the inconsistencies observed-till now-between conduction and spectroscopic measurements. The influence of defects on the bonding characteristics and the crystalline structure of STO was quantified, revealing that both VOand IHdefects lead to a significant polarization and strong tilting of the TiO6octahedra.
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acs.jpcc.2c04681
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Accepted/In Press date: 24 October 2022
e-pub ahead of print date: 24 October 2022
Published date: 3 November 2022
Additional Information:
Funding Information:
This work was supported by the National Science Centre in Poland (grant number UMO-2016/23/B/ST5/02137). The authors gratefully acknowledge the PSNC Poznan Supercomputing and Networking Center (Poznan, Poland) and the TASK Academic Computer Centre (Gdansk, Poland) for providing computer time and facilities. This research was supported by the PL-Grid Infrastructure. S.W. gratefully acknowledges the help of and valuable discussions with D. D. O’Regan.
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Local EPrints ID: 475374
URI: http://eprints.soton.ac.uk/id/eprint/475374
ISSN: 1932-7447
PURE UUID: e389dd06-e174-4fd0-9881-a842e420a545
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Date deposited: 16 Mar 2023 17:59
Last modified: 18 Mar 2024 03:15
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Author:
Szymon Winczewski
Author:
Tadeusz Miruszewski
Author:
Jarosław Rybicki
Author:
Maria Gazda
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