Study on Pyrolysis Characteristics of SF6 in a Trace-Oxygen (O2) Environment: ReaxFFSFO Force Field Optimization and Reactive Molecular Dynamics Simulation.

The ReaxFFSFO force field for a SF6-O2 system is developed based on the density functional theory (DFT) calculation data. Then, a series of molecular dynamics (MD) simulations were performed. The results show that the main oxygen-containing compounds that appeared in the MD simulation include SOF4, SOF2, and SO2F2. The relative quantitative relationship between SOF2 and SOF4 can be used to determine the fault temperature. Besides, under overheating conditions, O2 rarely undergoes a self-cracking process to generate free O atoms. Instead, the basic route for O2 to participate in the SF6 pyrolysis process is X + Y + O2 = XO + YO. Furthermore, the reactivity order of various groups to O2 is (SF2)* > (SF3)* > (SF4)* > F*, so O2 is more likely to participate in the reaction by attacking (SF3)* or (SF2)* groups. This study laid the foundation for the application of ReaxFF MD simulations to study the microscopic dynamic mechanism of SF6 pyrolysis in more complex systems.