title: Intermolecular Energy Transfer Dynamics at a Hot-Spot Interface in RDX Crystals.
abstract: 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.
authors.affiliation: Applied Research Institute, University of Illinois at Urbana-Champaign , Champaign, Illinois 61820, United States.
authors.forename: Kaushik
authors.initials: K
authors.lastname: Joshi
authors.affiliation: Applied Sciences Laboratory, Washington State University , Spokane, Washington 99210-1495, United States.
authors.forename: Martin
authors.initials: M
authors.lastname: Losada
authors.affiliation: Applied Research Institute, University of Illinois at Urbana-Champaign , Champaign, Illinois 61820, United States.
authors.forename: Santanu
authors.initials: S
authors.lastname: Chaudhuri