定常冲击波作用下六硝基六氮杂异伍兹烷(CL-20)/奥克托今(HMX)含能共晶初始分解机理研究

采用ReaxFF分子动力学方法同时结合多尺度冲击技术(MSST)模拟了4–10 km×s~(-1)定常冲击波加载下含能共晶CL-20/HMX沿不同晶格矢量的初始物理化学响应。获得了系统温度、压力、密度以及粒子速度的时间演化路径,以及初始分解路径,最终稳定反应产物和冲击雨贡纽等。研究结果表明:冲击波入射至含能共晶后,物理上依次经历诱导期、快压缩、慢压缩以及膨胀过程。快压缩和慢压缩过程分别对应反应物的快分解和慢分解。采用指数函数对反应物的衰减曲线进行拟合,并比较了共晶中反应物的衰减速率。整体上,随着冲击波速度的增加,反应物响应的时间逐渐提前,并且,冲击波沿各晶格矢量入射后,共晶中CL-20分子分解的响应时间均早于HMX。CL-20快分解阶段的衰减速率最高,HMX快分解的衰减速率居其次。相对于快分解阶段,慢分解阶段各反应物的衰减速率差异较小。含能共晶的初始反应路径是CL-20聚合形成二聚体,而冲击诱导共晶分解的初始反应路径是CL-20中N-NO_2键断裂形成NO_2。随后产生N_2O,NO,HONO,OH,H等中间小分子。最终稳定产物是N_2,H_2O,CO_2,CO和H_2。晶格矢量b,c方向冲击感度相同,低于晶格矢量a方向的感度。冲击诱导共晶中CL-20和HMX分解的最小冲击波速度(us)分别为6 km×s~(-1)和7 km×s~(-1)。采用冲击雨贡纽关系计算得到沿晶格矢量a,b,c冲击诱导CL-20/HMX共晶起爆的压力分别为16.52 GPa,17.41 GPa和17.41 GPa。爆轰压力范围介于36.75 GPa–47.43 GPa。

Study on the Initial Decomposition Mechanism of Energetic Co-Crystal 2, 4, 6, 8, 10, 12-Hexanitro-2, 4, 6, 8, 10, 12-Hexaazaiso-Wurtzitane (CL-20)/1, 3, 5, 7-Tetranitro-1, 3, 5, 7-Tetrazacy-Clooctane (HMX) under a Steady Shock Wave

CL-20 exhibits high energy density, but its high sensitivity limits its use in various applications. A high-energy and low-sensitivity co-crystal high explosive prepared around CL-20 has the potential to widen the application scope of CL-20 single crystals. The initial physical and chemical responses along different lattice vectors of the energetic co-crystal CL-20/HMX impacted by 4-10 km·s^-1 of steady shock waves were simulated using the ReaxFF molecular dynamics method combined with the multiscale shock technique (MSST). The temperature, pressure, density, particle velocity, initial decomposition paths, final stable reaction products, and shock Hugoniot curves were obtained. The results show that after application of the shock wave, the energetic co-crystals successively undergo an induction period, fast compression, slow compression, and expansion processes. The fast and slow compression processes correspond to the fast and slow decomposition of the reactants, respectively. An exponential function was adopted to fit the decay curve of the reactants and the decay rates of CL-20 and HMX were compared. Overall, with increasing shock wave velocity, the response time of the reactants was gradually advanced and that of CL-20 molecular decomposition in the co-crystal occurred earlier than that of HMX after the shock wave incident along each lattice vector. The decay rate of CL-20 was highest during the fast decomposition stage, followed by that of HMX. However, the decay rate of the reactants during the slow decomposition stage was similar. The initial reaction path of the energetic co-crystal involves the dimerization of CL-20, while the initial reaction path of the shock-induced co-crystal decomposition involves fracturing of the N-NO₂ bond in CL-20 to form NO₂. Then, small intermediate molecules such as N₂O, NO, HONO, OH, and H are formed. The final stable products are N₂, H₂O, CO₂, CO, and H₂. The shock sensitivities of the lattice vector in the b and c directions were the same, but lower than that of the lattice vector a direction. The minimum velocities (u_s) of the shock wave inducing CL-20 and HMX decomposition were 6 and 7 km·s^-1, respectively. Moreover, the particle velocities behind the shock waves on the three lattice vectors showed only minor differences. The shock-induced initiation pressures of CL-20/HMX along lattice vectors a, b, and c were 16.52, 17.41, and 17.41 GPa, respectively, as determined by the shock Hugoniot relation. The detonation pressure ranged from 36.75 to 47.43 GPa.