Computational study on the thermal decomposition mechanism and mechanical sensitivity of CL-20/4,5-MDNI

The cocrystallization technology of 6,8,10,12-hexanitro-2,4,6,8,10,12-hexazaisowurtzitane (CL-20) and 1-methyl-4,5-dinitroimidazole (4,5-MDNI) can reduce the mechanical sensitivity to achieve the safety application of CL-20 in the military and drilling industry. In this work, the decomposition mechanism of the CL-20/4,5-MDNI cocrystal was studied in detail through a series of reactive molecular dynamics (RMD) simulation, including the decomposition pathway and reaction kinetics. The potential energy and species were explored through RMD simulation during the decomposition process. It was found that the CL-20/4,5-MDNI cocrystal has a lower mechanical sensitivity relative to the pure CL-20 crystal (p-CL-20) for the larger hydrogen bonds ratio of the cocrystal by quantum chemistry method. In addition, it was noted that the calculated initial decomposition rate and heat release of the CL-20 in the cocrystal are lower than those of the p-CL-20, indicating that the reaction activity of the CL-20 was reduced by 4,5-MDNI. This work provides a theoretic guidance for the design and application of new energetic cocrystals.