Initial Decomposition of the Co-crystal of CL-20/TNT: Sensitivity Decrease under Shock Loading

Co-crystal of 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (CL-20)/2,4,6-trinitrotoluene (TNT) is a low-sensitivity and high-energy explosive obtained recently by combining 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (CL-20) and 2,4,6-trinitrotoluene (TNT) molecules by the co-crystallization technique. However, the underlying properties and decay mechanism remain unclear. In this work, we performed quantum-based multiscale shock simulation under shock loading by self-consistent charge density-functional tight binding method to study the initial chemical mechanism of CL-20/TNT. The results demonstrate that the temperature and pressure increase with decrease in volume when the shock strength increases constantly. The initial decomposition steps CL-20 and TNT molecules in co-crystal are consistent with the decomposition steps when they are pure crystal, N-NO2 bond cleavage at low velocity is observed while is inhibited at high velocity for CL-20 molecule, H transfer and C-NO2 bond break of TNT molecule are main initial decay step. Meanwhile, CL-20 decomposes faster than TNT and the releasing heat of CL-20 decomposition is transferred to TNT to increase the decomposition rate of TNT during the shock decomposition. Moreover, the evolution of the main stable products strongly depends on the shock strength. NO2 is the dominant primary intermediate resulting from a weak bond barrier, and CO, N-2, NO, among others are the main products determined by the shock strength. This study provides new insights into the initial decomposition mechanism of CL-20/TNT upon shock loading at the atomic level and has important implications for understanding and development of energetic materials.