Size-dependent shock response mechanisms in nanogranular RDX: a reactive molecular dynamics study

Understanding the shock initiation mechanisms of explosives is pivotal for advancing physicochemical theories and enhancing experimental methodologies. This study delves into the size-dependent shock responses of nanogranular hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) through nonequilibrium reactive molecular dynamics simulations. Utilizing the ReaxFF-lg force field, we examine the influence of the particle size on the decomposition dynamics of RDX under varying shock velocities. Our findings reveal that larger particles promote more significant RDX decomposition at lower velocities due to fluid jet formation and gas compression during void collapse. Conversely, smaller particles exhibit a higher average temperature and a faster decomposition rate under high-velocity shocks, attributed to their increased specific surface area. Detailed chemical reaction pathways are analyzed to elucidate the growth and initiation of reactions during shock waves. The results contribute to resolving the discrepancies observed in experimental studies of shocked granular explosives and provide a deeper understanding of the underlying mechanisms governing their behavior. This research offers valuable insights into the design and control of nano- and submicron-sized explosives with tailored sensitivity to external stimuli.