Structural evolution, sequential oxidation and chemical bonding in tri-yttrium oxide clusters: Y3Ox- and Y3Ox (x=0-6)

We report a systematic and comprehensive investigation on the electronic structures and chemical bonding of a series of tri-yttrium oxide clusters, Y3Ox-/0 (x = 0-6), using density functional theory (DFT) calculations. The generalized Koopmans' theorem was applied to predict the vertical detachment energies (VDEs) and simulate the photoelectron spectra (PES) for Y3Ox- (x = 0-6) clusters. A trend of sequential oxidation is observed from Y3O- to Y3O6-. All of these clusters tend to form structures with a capped oxygen atom. For Y3Ox-/0 (x = 2-4), the O atoms prefer the bridging sites of Y3Ox-/0, whereas the fifth O atoms for Y3O5-/0 are bonded to the terminal sites. In particular, the ground states of Y3O6-/0 are found to be interesting species, which may be viewed as molecular models for dioxygen activation by Y3O4-/0. sand pi-aromaticity is found in Y-3(-) by the molecular orbital analysis and Adaptive Natural Density Partitioning (AdNDP) analysis. Molecular orbital analyses are performed to analyze the chemical bonding in the tri-yttrium oxide clusters and to elucidate their electronic and structural evolution.