Dual-level direct dynamics studies on the reactions of OH radicals with SiH₃CH₃ and SiH₄

The multiple-channel reaction SiH₃CH₃ + OH → products (R1) and the single-channel reaction SiH₄ + OH → SiH₃ + H₂O (R2) have been studied by the direct dynamics method at the QCISD(T)/6-311++G(3df,3pd)//BH&H-LYP/6-311G(d,p) level. The rate constants for those reactions are calculated by improved canonical variational transition state theory (ICVT) with small-curvature tunneling (SCT) contributions in a temperature range 200-3000 K. For reaction (R1), H-abstraction from the SiH₃ group is the major channel. Since methyl substitution increases the reactivity of Si-H bond in silane, the rate constants of (R1) are larger than those of (R2) over the whole temperature region.