Looking for high energy density compounds among polynitraminecubanes

Based on fully optimized geometric structures at DFT-B3LYP/6-311G** level, we calculated electronic structures, heats of formation, strain energies, bond dissociation energies and detonation performance (detonation velocity and detonation pressure) for a series of polynitraminecubanes. Our results have shown that energy gaps of cubane derivatives are much higher than that of triaminotrinitrobenzene (TATB), which means that cubane derivatives may be more sensitive than TATB. Polynitraminecubanes have high and positive heats of formation, and a good linear relationship between heats of formation and nitramine group numbers was presented. As the number of nitramine groups in the molecule increases, the enthalpies of combustion values are increasingly negative, but the specific enthalpy of combustion values decreases. It is found that all cubane derivatives have high strain energies, which are affected by the number and position of nitramine group. The calculated bond dissociation energies of C-NHNO₂ and C-C bond show that the C-C bond should be the trigger bond in the pyrolysis process. It is found that detonation velocity (D), detonation pressure (P) and molecule density (ρ) have good linear relationship with substituented group numbers. Heptanitraminecubane and octanitraminecubane have good detonation performance over 1,3,5,7-tetranitro-1,3,5,7-tetraazacyclooctane (HMX), and they can be regarded as potential candidates of high energy density compounds (HEDCs). The results have not only shown that these compounds may be used as HEDCs, but also provide some useful information for further investigation.