A Hybrid Density Functional Theory Investigation of the (({ ext {CeO}}_2)_{6}) Clusters in the Cationic, Neutral, and Anionic States

We report a quantum-chemistry investigation of the cationic, neutral, and anionic oCeO2 6 clusters to obtain an atom-level understanding of the effects induced by the release or addition of a single electron on the physical and chemical properties of small oxide clusters. Our ab initio calculations are based on density functional theory (DFT) within the hybrid Heyd-Scuseria-Ernzerhof (HSE06) and semilocal Perdew-Burke-Ernzerhof (PBE) functional. Compared with PBE, the HSE06 functional changes the relative stability of the neutral oCeO2 6 isomers, in particular, for structures with small total energy differences, e.g., about 100 meV/fu, which can be explained by the enhancement of the exchange interactions. The addition of an electron to the oCeO2 6 clusters change the oxidation state of a single Ce atom from ? IV to ? III, which drives a local distortion and the formation of a small polaron near to the CeIII cation. In contrast, the release of an electron induces the formation of a localized hole on one of the O atoms combined with local structural distortions. For the anionic and cationic clusters in the putative global minimum configurations, we found a strain energy induced by the distortion of 1.00 and 1.31 eV, respectively.