Competitive Hydrogen Migration in Silicon Nitride Nanoclusters:Reaction Kinetics Generalized from Supervised Machine Learning

The rate coefficients for 52 hydrogen shift reactions forsilicon nitrides containing up to 6 atoms of silicon and nitrogen havebeen calculated using the G3//B3LYP composite method and statisticalthermodynamics. The overall reaction of substituted acyclic and cyclicsilylenes to their respective silene and imine species by a 1,2-hydrogenshift reaction was sorted by three different types of H shift reactionsusing overall reaction thermodynamics: (1) endothermic H shiftbetween N and Si:, (2) endothermic H shift between Si and Si:, and(3) exothermic H shift between Si and Si:. Endothermic H shiftreactions between Si atoms have one dominant activation barrier wherethe exothermic H shift reaction between Si atoms has two barriers and astable intermediate. The rate-determining step was determined to befrom the intermediate to the substituted silene, and then kineticparameters for the overall reaction were calculated for the two-steppathway. The single event pre-exponential factors, A??, and activation energies,Ea, for the three different classes of hydrogen shiftreactions of silicon nitrides were computed. The hydrogen shift reaction was explored for acyclic and cyclic monofunctional siliconnitrides, and the type of hydrogen shift reaction gives the most significant influence on the kinetic parameters. Using a supervisedmachine learning approach, the models for predicting the energy barrier of three different hydrogen shift reactions were generalizedand suggested based on selected descriptors.