Anisotropic Shock Sensitivity of Cyclotrimethylene Trinitramine (RDX) from Compress-and-Shear Reactive Dynamics

摘要

We applied the compress-and-shear reactive dynamicsud(CS-RD) simulation model to study the anisotropic shockudsensitivity of cyclotrimethylene trinitramine (RDX) crystals. Weudpredict that, for mechanical shocks between 3 and 7 GPa, RDX isudmost sensitive to shocks perpendicular to the (100) and (210)udplanes, whereas it is insensitive for shocks perpendicular to theud(120), (111), and (110) planes. These results are all consistent withudavailable experimental information, further validating the CS-RDudmodel for distinguishing between sensitive and insensitive shockuddirections. We find that, for sensitive directions, the shock impactudtriggers a slip system that leads to large shear stresses arising fromudsteric hindrance, causing increased energy inputs that increase theudtemperature, leading to dramatically increased chemical reactions.udThus, our simulations demonstrate that the molecular origin ofudanisotropic shock sensitivity results from steric hindrance toward shearing of adjacent slip planes during shear deformation. Thus,udstrain energy density, temperature rise, and molecule decomposition are effective measures to distinguish anisotropic sensitivities.udWe should emphasize that CS-RD has been developed as a tool to distinguish rapidly (within a few picoseconds) betweenudsensitive and insensitive shock directions of energetic materials. If the high stresses and rates used here continued much longerudand for larger systems, it would ultimately result in detonation for all directions, but we have not demonstrated this.