Structure and stability of oxygen adsorption on Sin (n = 5–10) clusters

Abstract

The structures, binding energies, and electronic properties of one oxygen atom (O) and two oxygen atoms (2O) adsorption on silicon clusters Si_n with n ranging from 5 to 10 are studied systematically by ab initio calculations. Twelve stable structures are obtained, two of which are in agreement with those reported in previous literature and the others are new structures that have not been proposed before. Further investigations on the fragmentations of Si_nO and Si_nO₂ (n = 5–10) clusters indicate that the pathways Si_nO → Si_n−1 + SiO and Si_nO₂ → Si_n−2 + Si₂O₂ are most favorable from thermodynamic viewpoint. Among the studied silicon oxide clusters, Si₈O, Si₉O, Si₅O₂ and Si₈O₂ correspond to large adsorption energies of silicon clusters with respect to O or 2O, while Si₈O, with the smallest dissociation energy, has a tendency to separate into Si₇ + SiO. Using the recently developed quasi-atomic minimal-basis-orbital method, we have also calculated the unsaturated valences of the neutral Si_n clusters. Our calculation results show that the Si atoms which have the largest unsaturated valences are more attractive to O atom. Placing O atom right around the Si atoms with the largest unsaturated valences usually leads to stable structures of the silicon oxide clusters.