Abstract
Elucidating the reasons for the reduced shock sensitivity of 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane/1-methyl-3,4,5-trinitropyrazole (CL-20/MTNP) compared with CL-20 is crucial for understanding the shock initiation of CL-20/MTNP co-crystalline explosives. In this study, molecular dynamics based on the ReaxFF-lg reactive force field was employed to simulate the propagation of the shock wavefront in the CL-20/MTNP co-crystal and corresponding single crystals. Thermodynamic properties and initial chemical reactions were analyzed using in-house programs. The results indicated that the pressure and temperature at the shock wavefront in the CL-20/MTNP co-crystal were not significantly different from those in the CL-20 crystal. During low- and medium-velocity impacts, the reactant molecules of the CL-20/MTNP co-crystal decayed slower than those of the corresponding single crystals. However, during high-velocity impacts, the decay rates of reactant molecules in the three crystals were similar. After the shock wavefront passed through, multiple CL-20 molecules of the CL-20 crystal simultaneously generated a large amount of NO(2). In the co-crystal, polymerization occurred primarily between CL-20 and MTNP molecules, which likely suppressed polymerization between CL-20 molecules, leading to the prolonged presence of NO(2) and extended generation of the intermediate product, which delayed the appearance of N(2). This may be the reason for the reduced impact sensitivity of CL-20/MTNP co-crystalline explosives.