Investigation on properties of energetic materials based on bis(4-nitropyrazole) bridged nitrogen-rich heterocycles

Energetic materials based on bis(4-nitropyrazole)-bridged nitrogen-rich heterocycles are designed, and their physical and chemical properties are fully investigated. Their heats of formation, detonation performance, and impact sensitivities are fully investigated. The results indicate that the addition of a tetrazole/-N₃ functional group contributes to an increase in the heats of formation of the designed compounds, while the incorporation of a tetrazole/-C(NO₂)₃ functional group is beneficial for enhancing their detonation performance. By comprehensively balancing energy performance and stability, candidate compounds A2 and E2 are screened out since these compounds possess better detonation performance and lower impact sensitivities than those of RDX. To further understand the physicochemical properties of the selected compounds, electronic structures such as frontier molecular orbitals and molecular electrostatic potential are simulated and analyzed.

The optimization of the designed compounds is performed with the Gaussian 16 program suite using the DFT-B3LYP method at the 6-311G(d,p) level. Multiwfn_3.8_dev is used to compute molecular surface properties. Employing the VMD program, the molecular electrostatic potential (ESP) distributions for compounds A2 and E2 are plotted. The initial decomposition mechanism and total decomposition process of A2 are investigated using the CASTEP code.