An ab Initio MO Study of the Thermal Decomposition of Chlorinated Monosilanes

The reactants, clusters, transition structures, and products for thevarious channels for the thermal decomposition of SiHkCl,, were optimized at the HF/6-31G(d) and MP2/6-31G(d,p) levels. The electron correlation contributions were calculated at the MP4/6-3 lG(d,p), MP4/6-31+G(Zdf,p), MP2/6-31 ++G(3df,3pd), and G-2 levels of theory. In the decomposition of SiH4, SiH2 + H2 is favored over SiH3 + H. For SiH3C1, the SiHCl + H2 channel is preferred over the SiH2 + HCl channel, with fragmentation into SiHzCl+ H and SiH3 + C1 lying significantly higher. The barriers for SiHzClz decomposition are Sic12 + H2 SiHCl + HCl < SiHCl2 + H < SiHzCl+ C1< SiH2 + C12. For SiHC13, decomposition into Sic12 + HCl is favored over Sic13 + H, with the SiHCl2 + C1 and SiHCl + Cl2 channels lying substantially higher. In tetrachlorosilane, Sic14 Sic13 + C1 is favored over Sic14 Sic12 + Cl2.