Looking for high energy density compounds among 1,3-bishomopentaprismane derivatives with CN, NC, and ONO(2) groups.

The paper concentrates on the "molecular design" of 1,3-bishomopentaprismane (BPP) derivatives with CN, NC, and ONO(2) groups as high energy density compounds (HEDCs). The heats of formation (HOFs), densities (rho), detonation velocities (D), and pressures (P) for a series of BPP derivatives, as well as their thermal stabilities, were calculated using density functional theory. The HOFs are high and increase with the substituted number (n) for BPP derivatives with CN and NC groups while are low and decrease with n for derivatives with ONO(2) group. D and P were estimated by using modified Kamlet-Jacobs equations based on the calculated HOFs and rho. The BPP derivatives with ONO(2) groups have excellent energetic properties to be HEDCs while the other two kinds of derivatives have relatively low rho, D, and P, revealing that CN and NC groups are not ideal substituents in the construction of HEDCs. The trigger bond in the pyrolysis process for CN and NC derivatives is the C-C bond in the skeleton, and these derivatives all have good thermal stability. In comparison, the trigger bond in the pyrolysis process for ONO(2) derivatives is the O-NO(2) bond, and these compounds are medium-stable. Taking both energetic properties and thermal stability into account, BPP derivatives with 6-8 ONO(2) groups are recommended as potential candidates of HEDCs. These results would provide basic information for the further studies of the title compounds.