Hybrid density functional theory description of oxygen vacancies in the CeO₂ (1 1 0) and (1 0 0) surfaces

In ceria the formation of oxygen vacancies plays a key role. Density functional theory, corrected for on-site Coulomb interactions (DFT + U) provides a reasonable description of oxygen vacancies, but has issues with the U dependence. We present a hybrid HSE06 study of oxygen vacancies in the (1 1 0) and (1 0 0) ceria surfaces. We find (i) the oxygen vacancy formation energy is larger with hybrid DFT compared with DFT + U, (ii) localised Ce³⁺ ions form and (iii) the position of the Ce³⁺ gap state is in good agreement with experiment. Our results provide important information for assessing the reliability of the DFT + U approach.