Reaction Molecular Dynamics Simulations of CL-20 Energetic Co-crystal under Shock

Co‐crystal technology is one of the effective methods to reduce the sensitivity of CL‐20. Studying the chemical reaction of CL‐20 co‐crystal under shock is helpful to understand the shock reaction mechanism of CL‐20 co‐crystal，which is of great significance to the safety evaluation and analysis of explosives. In this study，the molecular dynamics method of ReaxFF‐lg reaction force field and the non‐equilibrium loading method were used to simulate the shock compression process of CL‐20/DNT，CL‐20/ DNB and CL‐20/MDNT co‐crystals at 2-5 km·s-1 shock velocity. The thermodynamic evolution characteristics，initial chemical reaction path and product information of energetic co‐crystals after shock are obtained and compared with those of CL‐20. It’s discovered that the three co‐crystals of CL‐20/DNT，CL‐20/DNB and CL‐20/MDNT have a certain degree of shock sensitivity reduction，and the order of shock sensitivity of the three co‐crystals is CL‐20/MDNT>CL‐20/DNB>CL‐20/DNT. The decomposition reaction of the three co‐crystals all starts from the decomposition of CL‐20，and the decomposition rate of CL‐20 is faster than that of DNT，DNB and MDNT. At the shock velocity of 2 km·s-1，the polymerization reaction of CL‐20 co‐crystal occurs first. The polymerization reaction between CL‐20 and co‐crystal ligand molecules is earlier than that between CL‐20 molecules，and the reaction frequency is much higher than that between CL‐20 molecules. At the shock velocity of 3 km·s-1，the N - N and C-N bonds of CL‐20 are first broken，and the cage structure is destroyed. At the same time，NO2 is generated. NO2 generated by the initial bond breaking of CL‐20 further combines with the eutectic ligand molecules DNT，DNB and MDNT to reduce the concentration of the intermediate products of CL‐20 reaction，so as to achieve the desensitization effect. At the shock velocity of 4 or 5 km·s-1，the ring skeleton structure in CL‐20 is directly destroyed，the C‐N bond is broken，generating small molecular fragments，including N2，NO2，H2，CO2，H2O and other products. © 2024 Institute of Chemical Materials, China Academy of Engineering Physics. All rights reserved.