Structure and stability of silicon-oxide nanoclusters: the formation of reactive oxygen species on the surface
Oxidation of silicon nanoclusters going through all oxygen concentrations is explored from first principles using the evolutionary algorithm, structural and thermodynamic analysis. Calculations are performed for 90 clusters SinOm with n≤10 and m≤ 2n+9. Considering the Si7Om clusters with 0≤m≤23 as a model system, we analyze changes in their structure and energetics. The most involved processes take place at the cluster surface, where 12 characteristic groups of Si-O atoms (CGA), many of which are magnetic and relevant to reactive oxygen species (ROS), are distinguished. In all clusters oxidation shows itself as the consecutively appearing CGAs, which follow in the order dictated by their energetics and geometry. Thermodynamic analysis reveals clusters with ROS existing at the ambient conditions that rises biomedical issues.