Electronic Structure and Vibrational Modes of Cobalt Oxide Clusters CoOn (n = 1−4) and Their Monoanions

Abstract

The stationary points on the potential energy surfaces (PES) of cobalt oxide clusters were studied by the density functional theory, with the B1LYP exchange-correlation functional. A number of local minima were detected on the doublet, quartet, and sextet PES of CoOn (n = 1−4) and the singlet, triplet, and quintet PES of the corresponding anions. The normal vibrations of all optimized structures were calculated and interpreted in terms of group theory. The global minima and the low-lying local minima have been also examined by the coupled-cluster method with single and double substitutions and perturbational estimate of triple excitations, CCSD(T). The ground state of CoO is a quartet (4Δ), in agreement with previous assignments, while the ground state of CoO- is a quintet (5Δ). The oxides CoO2 are more stable than the peroxides Co(O2). The neutral oxide CoO2 in its ground state 6A1 is quasilinear; the monoanion in its 5Δg ground state is linear. Oxoperoxides OCo(O2) are more stable than oxides CoO3 and s...