Prediction on dielectric strength and boiling point of gaseous molecules for replacement of SF₆

Developing the environment-friendly insulation gases to replace sulfur hexafluoride (SF₆ ) has attracted considerable experimental and theoretical attentions but without success. A computational methodology was presented herein for prediction on dielectric strength and boiling point of arbitrary gaseous molecules in the purpose of molecular design and screening. New structure-activity relationship (SAR) models have been established by combining the density-dependent properties of the electrostatic potential surface, including surface area and the statistical variance of the surface potentials, with the molecular properties including polarizability, electronegativity, and hardness. All the descriptors in the SAR models were calculated using density functional theory. The substitution effect of SF₆ by various functional groups was studied systematically. It was found that CF₃ is the most effective functional group to improve the dielectric strength due to the large surface area and polarizability. However, all the substitutes exhibit higher boiling points than SF₆ because the molecular hardness decreases. The balance between E_r and T_b could be achieved by minimizing the local polarity of the molecules. SF₅ CN and SF₅ CFO were found to be the potent candidates to replace SF₆ in view of their large dielectric strengths and low boiling points. © 2017 Wiley Periodicals, Inc.