The Anisotropic Response and Initial Reaction Mechanism of a CL-20/MTNP High-Energy Cocrystal under Impact Loading

The CL-20/MTNP (1-methyl-3,4,5-trinitropyrazole) cocrystal exhibits the advantages of low sensitivity and high energy, and its reaction under shock demonstrates typical anisotropic characteristics. The anisotropy properties and the initial reaction mechanisms of the CL-20/MTNP (1-methyl-3,4,5-trinitropyrazole) cocrystal subjected to shock waves along the x[100], y[010], and z[001] directions at velocities of 8, 9, 10, and 11 km/s were investigated using the ReaxFF-lg force field combined with the multiscale shock technique (MSST). The results indicate that, upon shock impact on the CL-20/MTNP cocrystal, compressive deformation of its layered structure is initially observed. The primary reactions involve dimerization reactions between CL-20 and MTNP molecules within the same layer or adjacent layers, forming C-N, C-O, and N-N bonds. Because of the unique layered structure of the CL-20/MTNP cocrystal, the energy required for the dimerization reaction in the y[010] direction is lower than that in other directions, making it more prone to occur. Under the influence of shock waves at the same velocity, the reaction sensitivity in the y[010] direction is weaker, and its reaction rate is slower compared to other directions. The sensitivity orientation order of the CL-20/MTNP cocrystal is x[100] > z[001] > y[010]. This study can provide a theoretical basis for predicting the performance of energetic cocrystal systems and for designing molecular structures of energetic cocrystals.