Study of CeO2 and Its Native Defects by Density Functional Theory with Repulsive Potential

We investigated the native point defects in CeO2 by the density functional theory with repulsive potential (DFT+U) method and by use of a nonlinear core-corrected norm-conserving Ce pseudopotential. We find the neutral oxygen vacancy (VO0) in CeO2 to have a very low formation energy of only 0.39 eV in the O-poor limit. It is a deep donor with negative U behavior, stable only in its neutral and doubly positive states. The anion Frenkel defect is found to be the lowest energy disorder defect, with a formation energy of only 2.08 eV/defect site. These low formation energies arise from the improved transferability of our Ce pseudopotential for its +3 and +4 valence states. The negative U behavior of VO leads to excellent photocatalytic behavior, while the low formation energy of the anion Frenkel defect leads to a superior oxygen storage-and-release capability.