Atomistic Simulations of Shocks in HMX Crystals.

We are using large scale molecular dynamics simulations to study HMX crystals under shock compression. The objective is to obtain a fundamental understanding on the molecular scale of the dominant mechanisms of plastic relaxation and other dissipative processes in anisotropic molecular crystals. A fully flexible force field (Smith, G. D. and Bharadwaj, R. K.; \textit{J. Phys. Chem. B} \textbf{1999}, $103$, 3570) used in numerous preceding studies is used without modification in the present work. Initial results indicate that plastic deformation occurs even for weak shocks ($\sim $4GPa) on a time scale that is accessible to atomistic molecular dynamics ($\sim $100 ps for a 66,561 molecule system).