A double-U approach to more accurate metal adsorption energies on ceria

An empirical approach based on density functional theory (DFT)+U is proposed to provide adsorption energies for atoms of transition metals adsorbed on ceria that are more accurate than those found in the existing DFT literature. It involves applying an intermediate Hubbard U value to the Ce 4f states and another U value to the d states of the metal adatom that is optimized for each metal to match its calculated bulk cohesive energy with the experimental value. The results compare favorably with Campbell's calorimetric measurements of metal adsorption heats on CeO2(111). Thus, this approach produces metal adsorption energies on ceria that are more accurate in both the single-atom and the bulk limits. Furthermore, it preserves a common reference for Ce so that calculations involving different metals adsorbed on ceria, e.g., bimetallic and multimetallic clusters, can be analyzed on the same footing.