High-level ab initio and density functional theory study on reaction path and rate constant of the hydrogen abstraction reaction SiH₂Cl₂ + H → SiHCl₂ + H₂

Here we report high-level ab initio and density functional theory (DFT) results for reaction path and rate constant of the title hydrogen abstraction reaction. Based on ab initio UQCISD/6-311+G** and DFT BHLYP/6-311+G** levels, the electronic structure information including geometries, gradients, and force constants (Hessians) are obtained. Energies along the minimum energy path (MEP) are improved by a series of high-level ab initio G2//QCISD and PMP4/6-311+G(3df,2p)//BHLYP calculations. The properties of the reaction path by the DFT method are similar to those of that by the ab initio method. The reaction rate constants are calculated within 200-3000 K by canonical variational transition-state theory with the small-curvature tunneling correction (CVT/SCT) method. The results show that the DFT method is comparable with the ab initio method in obtaining reliable reaction rate constants for the reaction. The variational effect is small and in the lower-temperature range, the SCT effect is important for the reaction.