Density functional theory study of CL-20/Nitroimidazoles energetic cocrystals in an external electric field

Abstract

The external electric field (EEF) has a significant influence on the sensitivity of the energetic cocrystal materials. In order to find out the relationship between the EEF and sensitivity of energetic cocrystals 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane/1,4-dinitroimidazole (CL-20/1,4-DNI), 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane/1-methyl-2,4-dinitro-1H-imidazole (CL-20/2,4-MDNI) and 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane/1-methyl-4,5-dinitro-1H-imidazole (CL-20/4,5-MDNI). In this work, density functional theory (DFT) at B3LYP-D3/6–311 + G(d,p) and M062X-D3/ma-def2 TZVPP levels were employed to calculate the bond dissociation energies (EBDE) of selected N-NO2 trigger bonds, frontier molecular orbitals, electrostatic potentials (ESPs) and nitro group charges (QNO2) under different EEF. The results show that as the positive electric field increases, the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) energy gap and EBDE become smaller, and the local positive ESPs becomes larger so that the energetic cocrystals tends to have higher sensitivity. In addition, the linear fitting results show that the trigger bond length and nitro group charge changes are closely related to the EEF.