A Simple Group-Additivity Method to Predict the Dielectric Strength of Insulating Gases for Molecular Design

In view of the extremely significant impact on global warming of sulfur hexafluoride (SF
6
), extensive experimental and theoretical studies have been carried out to seek for the viable alternative insulation gas to SF
6
. The remarkable dielectric strength with respect to SF
6
is the most important criteria for molecular design on the novel gaseous dielectrics. Many structure-activity relationship models to predict the dielectric strength were proposed in literature. However, these techniques either showed unacceptable deficiency (e.g., weak correlation) or are too complicated (e.g., with the computer-intensive quantum chemical calculations) to be used conveniently. Because the phenomenological dielectric strength is usually related to the structural characteristics of a gas, it would be ideal to obtain dielectric strength straightforwardly from the functional groups. A group-additivity approach is proposed herein to estimate dielectric strength. A training set including 51 dielectric strengths were prepared by the critical evaluation of the experimental tests. Functional groups are developed systematically by minimization of the mean absolute deviation of the observed and calculated dielectric strengths. The present model shows better performance on average than the previous models. Several interesting trends in constructing novel dielectric gases have been found. A serial of eco-friendly dielectric molecules are rationally designed.