Density functional theory studies of effects of boron replacement on the structure and property of RDX and HMX

Abstract

AbstractIn this study, based on two model nitramine compounds hexahydro‐1,3,5‐trinitro‐1,3,5‐triazine (RDX) and octahydro‐1,3,5,7‐tetranitro‐1,3,5, 7‐tetrazocine (HMX), two series of new energetic molecules were designed by replacing carbon atoms in the ring with different amounts of boron atoms, their structures and performances were investigated theoretically by the density functional theory method. The results showed that the boron replacement could affect the molecular shape and electronic structure of RDX and HMX greatly, and then would do harm to the main performance like the heat of formation, density, and sensitivity. However, the compound RDX‐B2 is an exception; it was formed by replacing two boron atoms into the system of RDX and has the symmetric boat‐like structure. Its oxygen balance (4.9%), density (1.91 g/cm3), detonation velocity (8.85 km/s), and detonation pressure (36.9 GPa) are all higher than RDX. Furthermore, RDX‐B2 has shorter and stronger NNO2 bonds than RDX, making it possesses lower sensitivity (45 cm) and better thermal stability (the bond dissociation energy for the NNO2 bond is 204.7 kJ/mol) than RDX. Besides, RDX‐B1 and HMX‐B4 also have good overall performance; these three new molecules may be regarded as a new potential candidate for high energy density compounds.