Mechanistic Investigation of the Synergistic Effects of Mixed Gases Based on Density Functional Theory

Sulfur hexafluoride (SF6) gas is restricted from use due to its strong greenhouse effect. The development and application of new insulating gases have attracted significant attention. To avoid insulation failure caused by liquefaction, new insulating gases need to be diluted with buffer gases in the application. However, the synergistic ability of new insulating gases and buffer gases to suppress electron avalanche development is weak, leading to a relatively low dielectric strength of the new mixed insulating gases, which are only suitable for medium and low voltage electrical equipment. To enhance the dielectric strength of new mixed insulating gases, this study, based on density functional theory, investigates the interaction mechanisms between gas molecules. The configuration of the composite molecules formed by the interaction of mixed gas molecules is determined, and the stability of the composite configurations is analyzed. The changes in the electron density before and after the molecular binding are compared, and the correlation between the microscopic parameters of the gas molecule composites and the synergism of the mixed insulating gases is explored. The research results indicate that gas molecules can combine to form interaction configurations under intermolecular interactions. During the process of molecular binding to form interaction configurations, the electron density is redistributed, leading to differences in the microscopic parameters of the interaction configuration compared to the individual molecules. The interaction configuration has a stronger ability to suppress electron avalanche development than individual gas molecules, which results in an enhancement of the dielectric strength of the mixed gas beyond the linear sum of the dielectric strengths of the individual molecules. This gives rise to a significant synergistic effect in the mixed gas. Additionally, the ability of different interaction configurations to suppress electron avalanche development varies, causing the degree of dielectric strength enhancement in the mixed gas to differ, and consequently, the synergy among the mixed gases also varies.