Twin Induced Sensitivity Enhancement of HMX versus Shock: A Molecular Reactive Force Field Simulation

We report the early events of a twinned HMX crystal, as well as a perfect one for a comparison purpose, shocked with various velocities in the range of 6-10 km/s for 50 ps by molecular dynamic simulations using the ReaxFF reactive force field and the multiscale shock technique. The simulations show that the twin enhances the shock sensitivity remarkably, in agreement with our recent experimental observation. That is, it exhibits a lower shock initiation stress, higher decomposition velocities, more temperature, and stress increases under the same shock conditions, relative to the perfect crystal. In addition, we find the twinning plane is hottest and the temperature decreases in terms of the distance apart from it after shock loaded earlier, suggesting possible hot spots preferred there.