Investigating the stable structures of yttrium oxide clusters: Yn clusters as promising candidates for O2 dissociation†

Abstract

This study presents threshold photoionization (PI) spectra for a series of yttrium oxide clusters (YnOm, n = 2–8, m = 2–4) in the photon energy range of 192 to 300 nm (6.46 to 4.13 eV). Density functional theory (DFT) is employed to explore the stable structures of these clusters. For YnO2 clusters, experimental PI spectra are compared with calculated spectra for the lowest-energy and near-lowest-energy structural isomers. Stable structures contributing to the experimental PI spectra are identified. Experimentally corrected adiabatic ionization energies for YmO2 clusters are determined. The newly identified lowest-energy structure for Y2O2 differs from those in previous literature studies, while larger clusters show better agreement, primarily varying in oxygen binding sites. Molecular oxygen-absorbed configurations of yttrium oxide clusters are generally unstable or energetically unfavorable, with O2 activation occurring via charge transfer from yttrium to oxygen. Climbing image nudged elastic band (CI-NEB) calculations indicate that YnO2 forms in the ground state when an O2 molecule is absorbed onto low- or under-coordinated sites such as corners or edges of Yn clusters. This process involves the dissociation of the O–O bond, followed by the adsorption of individual O atoms at different sites on the Yn clusters. Analysis of the total density of states (TDOS) and partial density of states (PDOS) reveals an increased orbital density near the Fermi level, indicating a strong reaction affinity between Y and O atoms.