Chemical kinetics of hexamethyldisiloxane pyrolysis: A ReaxFF molecular dynamics simulation study

The pyrolysis kinetics of hexamethyldisiloxane (HMDSO) at various temperatures was studied using the reactive force field (ReaxFF) molecular dynamics simulations. Reaction rate constants and the main pyrolysis pathways were explored at the initial decomposition stage of HMDSO and intermediates decomposition stage. The activation energy and pre-exponential factor describing the reaction rate constants were obtained and further validated by experimental data and DFT theoretical calculations. The formation of C5H15OSi2 fragment by Si-C bond dissociation was dominant at the initial decomposition stage of HMDSO at the simulation temperatures of 2500-4000 K. The subsequent reaction pathways involved the formation of C5H14OSi2 and C4H11OSi2. After that, the pathways were different for 2500 and 3000 K. At 4000 K, small silicon-containing fragments were formed, including CH3Si, CH4Si, and C3H9Si, etc. The simulations also revealed that the major hydrocarbons generated during HMDSO pyrolysis were CH3 and CH4. Also, CH4 formation was more important in the end of HMDSO pyrolysis when simulation temperature was over 3500 K.