Modeling High Rate Impact Sensitivity of Perfect RDX and HMX Crystals by ReaxFF Reactive Dynamics

We report a methodology for rapid assessment of impact sensitivity of energetic materials which uses the ReaxFF reactive force field in reactive dynamics (RD) simulations of the high rate compression/expansion of a perfect energetic crystal. This approach is validated here to study the high rate impact sensitivity of 1,3,5-trinitrohexahydro-s-triazine (RDX) crystal and octahydro-1,3,5,7-tetrazocine (HMX) crystal at different phases (α, β, γ, and δ). These simulations found that for a compression rate of ∼8.76 km/s along the [100] direction, RDX crystals at lower volume compression ratios (x = 30, 35, 38%) led only to a few RDX molecules decomposing and only into primary products. However, at higher compression ratios (x ≥ 40%), all RDX molecules in the crystal decompose very quickly, leading to both primary and secondary decomposition reactions, including various intermediates such as NO2, NO, HONO, and OH and final products such as H2O, N2, CO, and CO2. For the various phases of HMX, these ReaxFF RD simu...