Theoretical studies on polynitro-1,3-bishomopentaprismanes as potential high energy density compounds

Based on the fully optimized molecular geometric structures at the DFT-B3LYP/6-31G* level, the densities (rho), detonation velocities (D) and pressures (P) for a series of polynitro-1,3-bishomopentaprismanes (PNBPPs), as well as their thermal stabilities, were investigated to look for high energy density compounds (HEDCs). The studied PNBPPs have high values of heats of formation (HOFs) and the magnitude is correlative with the number (n) and the space distance of nitro groups. D and P for PNBPPs were estimated by using modified Kamlet-Jacobs equations based on the calculated HOFs and rho. It is found that rho, D and P all increase with n and satisfy the group additivity rule. The calculations on the bond dissociation energies of C_NO(2) and C_C bonds indicate that both bonds are possible to be the trigger bond in the pyrolysis process, and this interesting phenomenon is related with the molecular structure, especially the strain energy of the skeleton. In conjunction with the energetic performances and thermal stabilities, PNBPPs with n=8-12 are recommended as the preferred candidates of HEDCs. These results would provide basic information for the further studies of PNBPPs.