Skelton, R and Walker, AM orcid.org/0000-0003-3121-3255 (2019) Interactions between bare and protonated Mg vacancies and dislocation cores in MgO. Physics and Chemistry of Minerals, 46 (5). pp. 471-485. ISSN 0342-1791
Abstract
Water can be incorporated into the lattice of mantle minerals in the form of protons charge-balanced by the creation of cation vacancies. These protonated vacancies, when they interact with dislocations, influence strain rates by affecting dislocation climb, pinning the dislocation, and, potentially, by altering the Peierls barrier to glide. We use atomic scale simulations to investigate segregation of Mg vacancies to atomic sites within the core regions of dislocations in MgO. Energies are computed for bare and V′′Mg protonated Mg vacancies occupying atomic sites close to ½ 〈110〉 screw dislocations, and ½ 〈110〉 {100} and ½ 〈110〉 {110} edge dislocations. These are compared with energies for equivalent defects in the bulk lattice to determine segregation energies for each defect. Mg vacancies preferentially bind to ½ 〈110〉 {100} edge dislocations, with calculated minimum segregation energies of − 3.54 eV for and − 4.56 eV for 2HxMg . The magnitudes of the minimum segregation energies calculated for defects binding to ½ 〈110〉 {110} edge or ½ 〈110〉 screw dislocations are considerably lower. Interactions with the dislocation strain field lift the threefold energy degeneracy of the 2HxMg defect in MgO. These calculations show that Mg vacancies interact strongly with dislocations in MgO, and may be present in sufficiently high concentrations to affect dislocation mobility in both the glide- and climb-controlled creep regimes.
Metadata
Item Type: | Article |
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Authors/Creators: |
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Copyright, Publisher and Additional Information: | (c) 2019, Springer-Verlag GmbH Germany, part of Springer Nature. This is an author produced version of a paper published in Physics and Chemistry of Minerals. Uploaded in accordance with the publisher's self-archiving policy. |
Keywords: | MgO; dislocation; cation vacancy; atomic-scale modeling |
Dates: |
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Institution: | The University of Leeds |
Academic Units: | The University of Leeds > Faculty of Environment (Leeds) > School of Earth and Environment (Leeds) > Inst of Geophysics and Tectonics (IGT) (Leeds) |
Funding Information: | Funder Grant number NERC NE/K008803/1 NERC NE/M000044/1 |
Depositing User: | Symplectic Publications |
Date Deposited: | 18 Dec 2018 15:31 |
Last Modified: | 04 Jan 2020 01:38 |
Status: | Published |
Publisher: | Springer Nature |
Identification Number: | 10.1007/s00269-018-01017-7 |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:140112 |