Bimolecular Initial Reactions in γ-RDX*

Shock compression of energetic molecular crystals often triggers solid-solid phase transitions to denser polymorphs (such as the γ polymorph of RDX) prior to onset of reactivity and shock-to-detonation transition. The more compact molecular arrangement in the unit cell of γ-RDX should affect the initial reactions leading to molecular decomposition. In this presentation, I will describe density functional theory (DFT) based molecular dynamics simulations and reaction path optimizations of initial decomposition reactions in γ-RDX subjected to hydrostatic pressures up to 20 GPa. These simulations predict that the dominant decomposition mechanism is bimolecular H transfer and simultaneous NO₂ loss rather than unimolecular N-N homolysis or HONO elimination