Dual-level direct dynamics studies on the reactions of tetramethylsilane with chlorine and bromine atoms

Abstract

The multiple-channel reactions Cl + Si(CH3)4 and Br + Si(CH3)4 are investigated by direct dynamics method. The minimum energy path is calculated at the MP2/6-31+G(d,p) level, and energetic information is further refined by the MC-QCISD (single-point) method. The rate constants for individual reaction channel are calculated by the improved canonical variational transition state theory with small-curvature tunneling correction over the temperature range 200–3,000 K. The theoretical three-parameter expression k1(T) = 9.97 × 10−13T0.54exp(613.22/T) and k2(T) = 1.16 × 10−17T2.30exp(−3525.88/T) (in unit of cm3 molecule−1 s−1) are given. Our calculations indicate that hydrogen abstraction channel is the major channel due to the smaller barrier height among feasible channels considered.