Density functional study of oxygen vacancy formation and spin density distribution in octahedral ceria nanoparticles.

We report plane wave basis density functional theory (DFT) calculations of the oxygen vacancies formation energy in nanocrystalline CeO2-x in comparison with corresponding results for bulk and (111) CeO2 surface. Effects of strong electronic correlation of Ce4f states are taken into account through the use of an effective on-site Coulomb repulsive interaction within DFT+U approach. Different combinations of exchange-correlation functionals and corresponding U values reported in the literature are tested and the obtained results compared with experimental data. We found that both absolute values and trends in oxygen vacancy formation energy depend on the value of U and associated with degree of localization of Ce4f states. Effect of oxygen vacancy and geometry optimization method on spatial spin distribution in model ceria nanoparticles is also discussed.