Carbon-free energetic materials: Computational study on nitro-substituted BN-cage molecules with high heat of detonation and stability

A new series of high-energy density materials (HEDMs) B₆N₆H_6-n(NO₂)_n (n = 1-6) are studied at the M06-2X/6-311++G∗∗, ωB97XD/6-311++G∗∗ and B3LYP/6-311++G∗∗ levels. Analysis of the structural changes caused by substituting the NO₂ and the electronic structures, such as electron localization function (ELF), Wiberg bond index (WBI), charge transfer and bond dissociation energies (BDE), provide important insights into the essence of the chemical characteristics and stability. Moreover, the Born-Oppenheimer molecular dynamic (BOMD) simulation is performed to verify their stability, which suggests that only the BN-cage derivatives with one and two nitro groups bonding with boron atoms (NO₂-1-1 and NO₂-2-1) can remain stable under ambient conditions. To predict the detonation performance and sensitivity of these two stable BN-cage energetic molecules accurately, the density, gas phase enthalpy of formation, enthalpy of sublimation, detonation performance, impact sensitivity and BDE are calculated systematically. The calculation results show that both NO₂-1-1 and NO₂-2-1 have a higher heat of detonation, higher value of h₅₀, and larger BDE of trigger bonds than CL-20.