NO2, OH和OH-对环四甲撑四硝胺初始热解的影响

在密度泛函理论的(DFT)B3LYP/6-31g(d)水平上, 优化得到了环四甲撑四硝胺(β-HMX)及其与高氯酸铵(AP)裂解产物NO2、OH及OH-分别形成复合物的各种稳定构型, 计算了β-HMX及各复合物中最弱的N—NO2键解离能. 结果发现: β-HMX与NO2、OH结合后构型变化不是很大, 但对称性降低; β-HMX与OH-结合后, HMX构型发生较大变化, 原有的对称性明显遭到破坏. 计算表明: NO2易与HMX骨架环上亚甲基(—CH2—)中的H作用,“置换”出H而引发HMX的热解, 从而改变了HMX的初始分解通道; OH对HMX的N—NO2键解离影响不大, 而OH-与β-HMX结合后其N—NO2键解离能比β-HMX降低近200 kJ·mol-1, 表明OH-对其裂解有明显的促进作用. NO2、OH-的存在可使HMX的分解温度大大降低.

Effects of NO2, OH and OH- on the Initial Pyrolysis of β-Octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine

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.