Abstract:

The structures of β-octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (β-HMX) and its complexes with the pyrolysis products (NO2, OH, OH-) of ammonium perchlorate (AP) were optimized at the B3LYP/6-31g(d) level of density functional theory (DFT). We obtained bond dissociation energies for N—NO2 in β-HMX and its complexes. We found that the geometrical configurations of HMX in the complexes with NO2 and OH were similar to the β-HMX structure but that the intrinsic symmetry decreases. The configurations of the OH- complexes are different and the original Ci symmetry is lost. Results further indicate that NO2 can easily capture a H from methylene on the HMX ring, which changes the initial pyrolysis channel of HMX. The influence of OH is negligible. The N—NO2 bond dissociation energies of OH- complexes decrease by about 200 kJ·mol-1 in comparison with that of β-HMX, which indicates that OH- can clearly promote the initial pyrolysis of β-HMX. The existence of NO2 and OH- can decrease the decomposition temperature of HMX greatly.

Key words: Density functional theory, HMX, Ammoniumperchlorate, Pyrolysis, Bond dissociation energy