Reactions of SiCl2 and SiHCl with H and Cl Atoms

Calculations have been carried out for the reaction of SiCl2 and SiHCl with H and Cl atoms. In each case, the stationary point geometries and harmonic frequencies were characterized using CASSCF/derivative methods and the cc-pVDZ basis set. Accurate energetics were obtained by combining the CCSD(T) results using the aug-cc-pVTZ basis set with an extrapolation to the basis set limit using the aug-cc-pVDZ, aug-cc-pVTZ, and aug-cc-pVQZ basis sets at the MP2 level. The geometries, energetics, and harmonic frequencies were used to obtain rate constants using conventional transition state theory or a Gorin-like model. In each case, we find direct abstraction pathways compete with an addition elimination pathway. In the case of SiClH + H, the two direct pathways are H abstraction which is barrierless and Cl abstraction with a barrier of 13.5 kcal/mol, whereas the addition elimination process has a barrrier of 26.9 kcal/mol. In the case of SiCl2 + H, the direct pathway is Cl abstraction with a barrier of 16.4 kcal/mol, whereas the addition elimination pathway has a barrier of 29.6 kcal/mol. In the case of SiClH + Cl, the direct pathway is H abstraction which is barrierless and the addition elimination pathway has a barrier of 2.0 kcal/mol.