Shock Waves in High-Energy Materials: The Initial Chemical Events in Nitramine RDX

We extend the reactive force field ReaxFF to describe the high energy nitramine RDX and use it with molecular dynamics (MD) to study its shock-induced chemistry. We studied shock propagation via nonequilibrium MD simulations at various collision velocities. We find that for high impact velocities (>6 km/s) the RDX molecules decompose and react to form a variety of small molecules in very short time scales (<3 ps). These products are consistent with those found experimentally at longer times. For lower velocities only NO₂ is formed, also in agreement with experiments.