Assessment of Density Functional Approximations for Highly Correlated Oxides: The Case of CeO₂ and Ce₂O₃

CeO₂ based materials are very attractive as catalytic components for industrial processes and environmentally friendly technologies; therefore, a reliable and computationally affordable theoretical description of the main properties of ceria is needed. In particular, the description of the interconversion between the Ce­(IV) and Ce­(III) oxidation states, on which lies the main chemical features of the cerium oxide, results in quite a challenge at the Density Functional Theory level. Here, we tested several density functional approximations, spanning from GGA to hybrid (Global, Meta-Global, and Range Separated Corrected) functionals, on the structural, vibrational, electronic, and thermochemical properties of bulk CeO₂ and Ce₂O₃. GGA and Meta-GGA xc best predict the thermochemical data, while the discrepancies increase with the introduction of the exact exchange in hybrid functionals. Overall, the Short Range Corrected and Global Hybrid functionals with a percentage of Exact Exchange between 16 and 25 give the best description of the crystal properties. Then, a group of the best performing functionals has been tested on the formation energy of an oxygen vacancy at the (111) CeO₂ surface. In general, increasing the amount of exact exchange in the hybrid functionals leads to a better description of the localized Ce 4f states, while the energy of formation of the O vacancy decreases, worsening compared to the experiment.