A DFT + U study of structure and reducibility of CenO2n−x (n ⩽ 4, 0 ⩽ x ⩽ n) nanoclusters

Abstract

Equilibrium structures, stability and reducibility of CenO2n−x (n⩽4, x=0∼4) nanoclusters have been studied using first principles DFT+U method. The planar rhombus Ce2O2 structure is found to be the building block for the most stable CenO2n−x clusters. The normalized binding energy of the cluster decreases linearly with increasing cluster size. The most stable stoichiometric CenO2n clusters are electronically in closed-shell configuration (singlet), while the non-stoichiometric CenO2n−x clusters are in a high spin state (triplet or quintet). The reduction energy, i.e., the energy required to remove an oxygen atom from a cluster, increases with the size and the extent of reduction. On the other hand, per electron based reduction energy for the cluster to reach the same formal oxidation state is independent of the cluster size.