The acid-base and redox reactivity of CeO sub(2) nanoparticles: Influence of the Hubbard U term in DFT + U studies

The interaction of small molecules with acid-base and redox centers in small Ce sub(21)O sub(42) nanoparticles has been theoretically investigated using the DFT + U approach with the PW91 functional and U = 0.2 and 4 eV, in order to determine the influence of the U value on the trends observed in se...

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Bibliographic Details
Published in:Surface science 2016-06, Vol.648, p.212-219
Main Authors: Boronat, Mercedes, Lopez-Ausens, Tirso, Corma, Avelino
Format: Article
Language:English
Subjects:
Adsorption
Defects
Lewis acid
Mathematical analysis
Nanoparticles
Surface chemistry
Trends
Vacancies
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Summary:The interaction of small molecules with acid-base and redox centers in small Ce sub(21)O sub(42) nanoparticles has been theoretically investigated using the DFT + U approach with the PW91 functional and U = 0.2 and 4 eV, in order to determine the influence of the U value on the trends observed in selected properties describing such interactions. CO adsorption at low coordinated Ce super(4 +) Lewis acid centers, water adsorption and dissociation at acid-base pairs, formation of oxygen vacancy defects by removal of an oxygen atom from the system, and interaction of molecular O sub(2) with such defects have been considered. The largest effect of the value of U is found for the description of the reduced Ce sub(21)O sub(41) nanoparticle. In all other cases involving stoichiometric and oxidized Ce sub(21)O sub(42) and Ce sub(21)O sub(43) systems, the trends in the calculated adsorption and reaction energies, optimized geometries, charge distribution, and vibrational frequencies are quite similar at the three levels considered.
ISSN:0039-6028
DOI:10.1016/j.susc.2015.10.047