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Linear-scaling density functional theory (DFT) simulations of point, Frenkel and Schottky defects in CeO2

Linear-scaling density functional theory (DFT) simulations of point, Frenkel and Schottky defects in CeO2
Linear-scaling density functional theory (DFT) simulations of point, Frenkel and Schottky defects in CeO2
CeO2 (ceria) is a material of significant industrial and technological importance, used in solid oxide fuel cells and catalysis. Here, we explore the usage of linear-scaling density functional theory as implemented in the ONETEP code, which allows to use larger simulation cells. By using DFT+U calculations we revise the defect chemistry of ceria, including point defects, Frenkel and Schottky defects.

We found that the ground state of an oxygen vacancy is associated to two neighbouring reduced cerium sites. A cerium vacancy is the least favourable point defect, where holes localise on neighbouring oxygen sites. It is more favourable to displace an oxygen interstitial defect away from the octahedral interstitial site, with the formation of a stable peroxide species. Our simulations show that a cerium interstitial is best accommodated in the octahedral interstitial site, as this minimises the distortion of the lattice.

Placing a vacancy and an interstitial defect at a separation of 5.18 Å for the OF<110> and 4.77 Å for the CeF<111>, stable Frenkel defects can be formed. We also studied the effect of different supercell size on the energetic ordering of Schottky defects, where the S<111> is more favourable than the S<110> for a given simulation cells containing 324 or more atoms.
0927-0256
Anwar, Nabeel
661d9a85-a01e-43d2-b5b6-5eb5c4029385
Harker, Robert M.
d839c95b-57c0-4919-a5c2-577bed87a3a8
Storr, Mark T.
a26917cb-4b1d-4ca7-a6bb-25eb89e6e451
Molinari, Marco
e897d403-d1b5-47db-8b63-dcd1f39a516c
Skylaris, Chris-Kriton
8f593d13-3ace-4558-ba08-04e48211af61
Anwar, Nabeel
661d9a85-a01e-43d2-b5b6-5eb5c4029385
Harker, Robert M.
d839c95b-57c0-4919-a5c2-577bed87a3a8
Storr, Mark T.
a26917cb-4b1d-4ca7-a6bb-25eb89e6e451
Molinari, Marco
e897d403-d1b5-47db-8b63-dcd1f39a516c
Skylaris, Chris-Kriton
8f593d13-3ace-4558-ba08-04e48211af61

Anwar, Nabeel, Harker, Robert M., Storr, Mark T., Molinari, Marco and Skylaris, Chris-Kriton (2023) Linear-scaling density functional theory (DFT) simulations of point, Frenkel and Schottky defects in CeO2. Computational Materials Science, 229, [112396]. (doi:10.1016/j.commatsci.2023.112396).

Record type: Article

Abstract

CeO2 (ceria) is a material of significant industrial and technological importance, used in solid oxide fuel cells and catalysis. Here, we explore the usage of linear-scaling density functional theory as implemented in the ONETEP code, which allows to use larger simulation cells. By using DFT+U calculations we revise the defect chemistry of ceria, including point defects, Frenkel and Schottky defects.

We found that the ground state of an oxygen vacancy is associated to two neighbouring reduced cerium sites. A cerium vacancy is the least favourable point defect, where holes localise on neighbouring oxygen sites. It is more favourable to displace an oxygen interstitial defect away from the octahedral interstitial site, with the formation of a stable peroxide species. Our simulations show that a cerium interstitial is best accommodated in the octahedral interstitial site, as this minimises the distortion of the lattice.

Placing a vacancy and an interstitial defect at a separation of 5.18 Å for the OF<110> and 4.77 Å for the CeF<111>, stable Frenkel defects can be formed. We also studied the effect of different supercell size on the energetic ordering of Schottky defects, where the S<111> is more favourable than the S<110> for a given simulation cells containing 324 or more atoms.

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Accepted/In Press date: 20 July 2023
e-pub ahead of print date: 17 August 2023
Published date: 17 August 2023

Identifiers

Local EPrints ID: 481267
URI: http://eprints.soton.ac.uk/id/eprint/481267
ISSN: 0927-0256
PURE UUID: b946956e-ac89-446a-8f9e-d32ddbcc3e93
ORCID for Nabeel Anwar: ORCID iD orcid.org/0000-0003-1221-9256
ORCID for Chris-Kriton Skylaris: ORCID iD orcid.org/0000-0003-0258-3433

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Date deposited: 21 Aug 2023 17:03
Last modified: 30 Aug 2024 02:00

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Contributors

Author: Nabeel Anwar ORCID iD
Author: Robert M. Harker
Author: Mark T. Storr
Author: Marco Molinari

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