Thermochemical and Performance Properties of NO2-Substituted Borazines as New Energetic Compounds with High Thermodynamic Stability

The structural isomers of nitroborazines were optimized at M062X/6-311++G** level of theory. The effects of the NO2 group on the molecular volume, molecular surface area, crystal density, positive, negative and total average potentials, variances, average deviation and electrostatic balance parameter on the molecular surface were considered. In addition, some important thermodynamic properties of these compounds, such as gas phase and condensed phase enthalpies of formation (ΔfH° (g) and ΔfH° (c)), and the enthalpy of sublimation (ΔH° sub), were calculated. It was found that the crystal densities (ρ) are in the range 1.4471.902 g/cm3. These values are slightly smaller than the corresponding values of their carbon analogues (except for the mononitro compounds). Meanwhile, the values of ρ for B-substituted, di- and trinitroborazines are larger than the related N-substituted compounds. The calculated values of ΔH° sub are in the range 20.1-30.4 kcal/mol. The calculated values of ΔfH° (g) and ΔfH° (c) for the B-substituted nitroborazines are more negative than those for the N-substituted ones. The stability sequence of the hydrogen bonded network structures of nitroborazines in the condensed phase is: dinitroborazine > mononitroborazine > trinitroborazine. The detonation pressure and velocity of these compounds were also calculated. Nitroborazines can be introduced as energetic compounds with high thermodynamic stability and relatively low detonation performance.