Low-level settings consist on using a single O-Ce-O tri-layer to represent the ceria surface, which is kept fixed to the corresponding bulk positions. Spin-polarization is not allowed at this level, and the energy difference thresholds controlling the convergence of the self-consistent field are set to 10 -4 eV for the energy cut-off of SCF iterations (EDIFF), the plane wave basis set energy cut-off is set for the minimum energy cut-off recommended in the PAW potentials for each atomic species (300 eV), and the PREC=Low flag of VASP.