Theoretical study and rate constants calculation for the reactions of SiH3 radical with SiH3CH3 and SiH2(CH3)2.

The multiple-channel reactions SiH(3) + SiH(3)CH(3) --> products and SiH(3) + SiH(2)(CH(3))(2) --> products are investigated by direct dynamics method. The minimum energy path (MEP) is calculated at the MP2/6-31+G(d,p) level, and energetic information is further refined by the MC-QCISD method. The rate constants for individual reaction channels are calculated by the improved canonical variational transition state theory (ICVT) with small-curvature tunneling (SCT) correction over the temperature range of 200-2400 K. The theoretical three-parameter expression k(1)(T) = 2.39 x 10(-23)T(4.01)exp(-2768.72/T) and k(2)(T) = 9.67 x 10(-27)T(4.92)exp(-2165.15/T) (in unit of cm(3) molecule(-1) s(-1)) are given. Our calculations indicate that hydrogen abstraction channel from SiH group is the major channel because of the smaller barrier height among eight channels considered.