Interaction of hydrogen with actinide dioxide (111) surfaces

James T Pegg; Ashley E Shields; Mark T Storr; David O Scanlon; Nora H de Leeuw

doi:10.1063/1.5087577

Interaction of hydrogen with actinide dioxide (111) surfaces

J Chem Phys. 2019 Apr 7;150(13):134701. doi: 10.1063/1.5087577.

Authors

James T Pegg¹, Ashley E Shields², Mark T Storr³, David O Scanlon¹, Nora H de Leeuw¹

Affiliations

¹ Department of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ, United Kingdom.
² Oak Ridge National Laboratory, One Bethel Valley Road, Oak Ridge, Tennessee 37831, USA.
³ Atomic Weapons Establishment (AWE) Plc, Aldermaston, Reading RG7 4PR, United Kingdom.

PMID: 30954055
DOI: 10.1063/1.5087577

Abstract

The interaction of atomic and molecular hydrogen with actinide dioxide (AnO₂, An = U, Np, Pu) (111) surfaces has been investigated by DFT+U, where noncollinear 3k antiferromagnetic behaviour and spin-orbit interactions are considered. The adsorption of atomic hydrogen forms a hydroxide group, 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, shown to be due to kinetic rather than thermodynamic factors. As a barrier to the formation of a second hydroxyl group, an unusual charge distribution has been shown. This could be a limitation of a (1·1) unit cell method or an artefact of the systems. The recombination of hydrogen ions on the AnO₂ (111) surfaces is favoured over hydroxide formation.