Microscale impact response characteristics of ε-CL-20: A multiscale simulation study with coupled force fields

S Ren and W Yang and Q Gan and M Xia and YJ Wang and G Li and CJ Tong and L Liang and WB Zhang, COMBUSTION AND FLAME, 281, 114441 (2025).

DOI: 10.1016/j.combustflame.2025.114441

Exploring the microscopic mechanism of critical initiation conditions is a challenging task in shock research on energetic materials. Herein, a multiscale impact simulation of hexanitrohexaazaisowurtzitane (epsilon- CL-20) was conducted within a velocity range of 8.0 similar to 10.0 km/s by coupling the NNP-SHOCK force field with the ReaxFF-lg force field. Using peak pressure as a stage division indicator, the impact initiation process was quantitatively divided into two stages: impact compression and intense reaction. Among the large variety of epsilon-CL-20 decomposition products, CO2 content was identified as a key metric to reflect the initial reaction process of epsilon-CL-20, rather than the initial product NO2. The correlation between the change in CO2 quantity and the change in unit cell pressure is particularly high when the shock wave velocity is below the critical shock initiation velocity (9.1 km/s) of CL-20. Correspondingly, the calculated critical decomposition rate of CL-20 reaches 9.451 ps(-1) when subjected to a critical detonation velocity. In addition, reaction network diagrams of epsilon-CL-20 and its typical final products (CO2, H2O, and N-2) were drawn to clarify the initial transformation pathways of epsilon-CL-20 and to determine the intrinsic relationships among the chemical reactions of CO2, H2O, and N-2.

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