Analysis of Intrinsic Defects in CeO2 Using a Koopmans-Like GGA+U Approach

Abstract

We have investigated the formation of intrinsic defects in CeO2 using density functional theory with the generalized gradient approximation (GGA) corrected for on-site Coulombic interactions (GGA+U). We employed an ab initio fitting procedure to determine a U{O2p} value that satisfies a Koopmans-like condition and obtained a value of U{O2p} = 5.5 eV. We subsequently demonstrated that by applying GGA+U to the O2p states, in addition to the Ce4f states, we were able to model localized holes in addition to localized electrons, thus improving the description of p-type defects in CeO2. Our results show that under oxygen-poor conditions the defects with the lowest formation energy are oxygen vacancies, while oxygen interstitials, which form peroxide ions, will be more favorable under oxygen-rich conditions. We carried out temperature and pressure dependence analyses to determine the relative abundance of intrinsic defects under real-world conditions and determined that oxygen vacancies will always be the domina...