H+、NH+4对HMX的N—NO2键解离能的影响

采用密度泛函理论的B3P86/6-31G**方法, 优化了β-HMX及其与H⁺、NH^+₄分别形成的复合物的稳定结构, 计算了β-HMX以及复合物中最弱的N—NO₂键解离能. 结果发现, HMX与H⁺、NH^+₄形成复合物后, 使HMX的构型产生较大变化; 与H⁺结合后, HMX的一个N—NO₂键显著伸长, 键级变小; 但与NH^+₄形成复合物后, HMX中键级最小的N—NO₂键长变化不大. 键解离能计算表明, 同β-HMX相比, 与H⁺形成的两种复合物中N—NO₂键解离能分别降低了近20 和82 kJ·mol^-1, 而HMX与NH^+₄形成的复合物中N—NO₂键解离能仅降低了约8 kJ·mol^-1, 表明H⁺对β-HMX的N—NO₂键的初始热裂解反应有促进作用, 而NH^+₄影响不明显.

Effect of H+ and NH4+ on the N-NO2 Bond Dissociation Energy of HMX

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.