Study on the mechanism of the effect of temperature on the decomposition reaction of SF (n = 1-6) under discharge conditions.

The study on the mechanism of the effect of temperature on the decomposition reaction of SF (n = 1-6) under discharge conditions is very important in studying the potential fault of SF high voltage switch equipment and perfecting the chemical kinetic model of SF discharge. In this paper, structural optimizations, thermal correction to Gibbs free energy for the reactants, and products were performed at the B3LYP/6-311 +  + G(d,p) theory level. The single-point energies of all species were collected at the CCSD(T)/aug-cc-PVTZ level. The electric and thermal decomposition mechanism of SF under discharge conditions of 298-10,000 K were studied, respectively. The conclusion drawn was that in the temperature range of 298-10,000 K, the thermal decomposition homopolytic reaction △G began to decline from 200 kJ/mol, while the △G of the other two heterogenous reactions began to decrease from 1000 kJ/mol and 2000 kJ/mol, showing a downward trend of an almost similar slope. The electrolysis of SF is related to electron energy. When the electron energy is low, SF + e → SF series reactions occur, and △G of R12, R20, R28, R36, and R44 increases with temperature rise, while △G of R4 decreases with temperature. When the electron energy is high, one of SF  → SF  + F, SF  → SF + F, and SF  → SF + F + e will occur, and the reactions that occur at various temperature ranges as the temperature rises vary. When the second electron hits the SF, the SF  + e → SF  + F reaction will occur. The △G of this reaction slowly decreases with an increase in temperature. This study in clearer terms explains the decomposition process and mechanism of SF at different temperatures.