Intermolecular Energy Transfer Dynamics at a Hot-Spot Interface in RDX Crystals

The phonon mediated vibrational up-pumping mechanisms assume an intact-lattice and Climbing of a vibrational ladder using strongly correlated multiphonon dynamics under equilibrium or near-equilibrium conditions. Important dynamic processes far from equilibrium in regions of large temperature gradient after the onset of decomposition reactions in-energetic Solids are relatively unknown. In this work, we-present a classical molecular dynamics (MD) simulation-based study of such processes using a nonreactive and a reactive potential to study a fully reacted and, unreacted zone in RDX (1,3,5-trinitro-1,3,5-triazocyclohexane) crystal under nonequilibrium conditions. The energy transfer rate is,evaluated as a function Of temperature difference between the reacted and unreacted regions, and for different widths and cross-sectional area of unreacted RDX layers. VibratIonal up-pumping processes probed using velocity, autocorrelation functions indicate that the mechanisms at high-temperature interfaces are quite different from the standard phonon-based Models proposed in current literature. In particular, the up-pumping of high-frequency vibrations are seen in the presence of small molecule collisions at-the hot-spot interface with strong contributions from bending modes. It also explains Some major difference in the order of-decomposition of C-N and N-N bonds as seen in recent literature on initiation-chemistry: