Density functional theory, corrected for on-site Coulomb interactions (DFT + U), was used to study the defects formed in ceria (111) and (110) surfaces doped with La. To describe consistently the defect formed with substitutional La3 + doping at a Ce4 + site DFT and DFT + U were used, with U = 5eV for Ce 4f states and U = 7eV for O 2p states. When La3+ was substituted at a Ce3 + site, an LaCe’ + OO• defect state, with an oxygen hole, was formed at both surfaces; but only with the DFT + U approach. The formation energy of an oxygen vacancy in a structure with two La dopants in their most stable distribution was reduced over the undoped surfaces but remained positive. Formation of an oxygen vacancy resulted in the appearance of a reduced Ce3 + cation and a compensated oxygen hole, instead of compensation of both oxygen holes, which was typical of metal oxides doped with lower valence cations. It was tentatively suggested that the key role in the formation of this unusual defect was played by cerium and arose from the ease with which cerium could be reduced, as compared to other metal oxides.

Doping of Ceria Surfaces with Lanthanum: a DFT + U Study. I.Yeriskin, M.Nolan: Journal of Physics - Condensed Matter, 2010, 22[13], 135004