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Interaction of Hydrogen with Actinide Dioxide (111) Surfaces

preprint
revised on 22.02.2019, 14:15 and posted on 22.02.2019, 16:31 by James Pegg, Ashley E. Shields, Mark T. Storr, David Scanlon, Nora De Leeuw
The interaction of atomic and molecular hydrogen with the actinide dioxide (AnO2, An = U, Np, Pu) (111) surfaces has been investigated by DFT+U, where noncollinear 3k antiferromagnetic (AFM) behaviour and spin-orbit interactions (SOI) are considered. The adsorption of atomic hydrogen forms a hydroxide group, and is coupled to the reduction of an actinide ion. The energy of atomic hydrogen adsorption on the UO2 (0.82 eV), NpO2 (-0.10 eV), and PuO2 (-1.25 eV) surfaces has been calculated. The dissociation of molecular hydrogen is not observed, and shown to be due to kinetic rather than thermodynamic factors. As a barrier in the formation of a second hydroxyl group, an unusual charge distribution has been shown. This is possibly a limitation of a (1·1) unit cell method. The recombination of hydrogen ions on the AnO2 (111) surfaces is favoured over hydroxide formation.

Funding

EP/G036675

EP/K016288

History

Email Address of Submitting Author

pegg.james.t@gmail.com

Institution

University College London

Country

United Kingdom

ORCID For Submitting Author

0000-0002-6743-8651

Declaration of Conflict of Interest

None

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in The Journal of Chemical Physics

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