Early Decay Mechanism of Shocked ε‑CL-20: A Molecular Dynamics Simulation Study

ε-2,4,6,8,10,12-Hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (CL-20) is currently the most powerful explosive commercially available. Nevertheless, the early decay events of shocked ε-CL-20 still remain unclear. We perform quantum based self-consistent charge density-functional tight-binding molecular dynamics simulations, in combination with the multiscale shock simulation technique, to reveal the events with four specified shock velocities (Us) of 8 to 11 km/s. We find that the temperature and pressure increases and that the volume reduction is enhanced with increasing shock strength. The ring opening is observed to trigger molecular decay at all four shock conditions; while the sufficient NO₂ fission is observed at Us = 8 and 9 km/s, and strongly inhibited at Us = 10 and 11 km/s. Moreover, the evolution of main chemical species, such as active intermediates, stable products, and clusters, is strongly dependent on the shock strength. NO₂ and H are dominant in the primary intermediates, responsible for weak and strong shock, respectively; CO₂ and N₂, as well as water, are the main stable products with a population gradation determined by the shock strength; and the bigger clusters with longer durations are found to be caused by the stronger shock, and their fast dissociation mainly undergoes through the ring opening. Besides, it is found that ε-CL-20 possesses weak anisotropy in the above-specified Us range. This work will enrich the knowledge of shocked energetic materials, in particular, the important energetic materials.