Establishment of a Reax force field to study SF6 gas over-thermal decomposition

Abstract

This paper focuses on the problem of missing parameters in the Reax force field containing S and F elements. First, density functional theory was used to scan SF6 and low-fluoride sulfide molecules to obtain the basic dataset for the Reax force field. The Monte Carlo method was then used to perform fitting optimization and quality verification of the established force field. Based on the established force field, molecular dynamics studies were carried out on the over-thermal decomposition of a SF6 gas-insulating medium, and infrared spectra were obtained, describing the vibration characteristics of SF6 and low-fluoride sulfide molecules. According to the vibration modes revealed by the infrared spectra, a potential-energy surface scan was performed. This paper focuses on the analysis of the total energy, potential energy and kinetic energy of SF6 and low-fluoride sulfide molecules moving at different temperatures. The results show that the energy error of the established force field is about 10% when describing the bonding and breaking processes of SF6, SF5, SF4, SF3 and SF2 molecules, which verifies the reliability of the reactive force field method when used to describe molecular behavior. The research work detailed in this paper lays the foundation for the next systematic study of the microscopic physical mechanisms of SF6 over-thermal decomposition.