Theoretical Study on CL-20-Based Cocrystal Energetic Compounds in an External Electric Field

An external electric field has great effects on the sensitivity of cocrystal energetic materials. In order to find out the relationship between the external electric field and sensitivity of cocrystals 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane/benzotrifuroxan (CL-20/BTF), 2,4,6,8, 10,12-hexanitro-2,4,6,8, 10,12-hexaazaisowurtzitane/3,4-dinitropyrazole (CL-20/DNP), and 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane/1-methyl-3,5-dinitro-1,2,4-triazole (CL-20/MDNT), density functional theory at B3LYP-D3/6-311+G(d,p) and M062X-D3/ma-def2 TZVPP levels was employed to calculate frontier molecular orbitals, atoms in molecules (AIM) electron density values, bond dissociation energies (BDEs) of the N-NO2 bond, impact sensitivity (H-50), electrostatic potentials (ESPs), and nitro group charges (Q(NO2)) in this work. The results show that a smaller highest occupied molecular orbital-lowest unoccupied molecular orbital gap and the BDEs, as well as H-50, tend to have a larger sensitivity along with the positive directions in the external electric field. Moreover, a smaller local positive ESP (V-s max) leads to better stability in the negative electric field. The sensitivity of cocrystal molecules decreases gradually in the negative external electric field with the increase of negative nitro group charges. Finally, the change in the bond lengths, AIM electron density values, and nitro group charges correlate well with the external electric field strengths.