Group Additivity Theoretical Model for the Prediction of Dielectric Strengths of the Alternative Gases to SF6

Dielectric strength is one of the most parameters for the design and discovery of novel eco-friendly replacement gases for SF6. Various structure-activity relationship models had been widely used to predict the dielectric strength on the basis of the quantum chemistry calculated descriptors, which are computationally demanding and usually involve significant uncertainties and incapability of treating some specific compounds. In order to predict the dielectric strength of a gas straightforwardly, group additivity method was proposed in this work. Within the first-order approximation, the direct summation of the optimized individual contributions of the functional groups gives the overall dielectric strength. In comparison with a total of 65 insulating gases, the agreement between group additivity and experimental data is excellent. The mean absolute and relative deviations are 0.0656 and 6.28%, respectively. The correlation coefficient between theory and experiment is 0.9879, which are all superior to the structure-activity relationship models. The result reveals that inducing the unsaturated group or cyclic moiety and substituting the isolated CHx and CF by CF3, OCF3, and SCF3 is efficient to improve the dielectric strength.