Density functional theory direct dynamics studies on the hydrogen abstraction reactions of SiHCl₃ + H → SiCl₃ + H₂ and SiH₃Cl + H → SiH₂Cl + H₂

The reliability of density functional theory (DFT) direct dynamics method is tested for calculating reaction paths and rate constants of the title reactions. The electronic structure information including geometries, gradients, and force constants (Hessians) is calculated by the DFT BHLYP method with the 6-311+G**basis set. Energies along the minimum energy path (MEP) are improved by a series of single-point PMP4/6-311 +G(3df,2p)//BHLYP calculations. By canonical variational transition state theory with small-curvature tunneling correction (CVT/SCT) method, the rate constants of the reactions are calculated within 200-3000 K, for which accurate values are obtained in the experimentally measured temperature ranges. Based on the DFT direct dynamics calculation, the stationary points, reaction-path properties, and reactivity trends of the title reactions are compared with those of SiH₂Cl₂ + H → SiHCl₂ + H₂. This paper provides conclusive comparison about the effect of successive chlorine substitution on the hydrogen abstraction reactions of H atoms with chlorosilanes.