Abstract: The structure of β-HMX and several complexes with H⁺ or NH^+₄ were optimized using the density functiona theory(DFT)at the B3P86/6-31G** level. Meanwhile, the bond dissociation energies of the weakest N—NO₂ for β-HMX and the complexes were obtained by the same calculation method. It was found that the geometrical configuration of the HMX in the complexes differed significantly from that of β-HMX. On the other hand, one of the N—NO₂ bonds of HMX was activated due to the combination of H⁺ with HMX, but this activation was unobvious for the complexes with NH^+₄ . The N—NO₂ bond dissociation energies of two complexes with H⁺ decreased about 20 and 82 kJ·mol^-1, respectively, in comparison with that of β-HMX. However, the N—NO₂ bond dissociation energy for the complex with NH^+₄ decreased only about 8 kJ·mol^-1. It indicated that the H⁺ could promote the initial thermal decomposition of N—NO₂ bond of β-HMX, but this initial decomposition was slightly influenced by NH^+₄.

Key words: HMX, Bond dissociation energy, Thermal decomposition, DFT