-------------------------------------------------------------------- SEMINAR OF THE LABORATORY FOR COMPUTER DESIGN OF MATERIALS Institute for Computational Sciences and Informatics -------------------------------------------------------------------- MOLECULAR DYNAMICS SIMULATIONS OF SHOCK AND DETONATION Sam Trevino, Betsy M.Rice, John Grosh and William Mattson Army Research Laboratory Although the phenomenon of detonation has been explored for over a century, microscopic details of the chemical and physical changes occurring during the detonation cannot be measured due to the small time and length scales over which the event occurs. Measurements are additionally hampered by the enormous energy release during the detonation. Molecular dynamics is not hampered by these considerations. We present two series of molecular dynamics simulations of the detonation phenomenon. The chemistry which is modeled by the inter-atomic and inter-molecular potentials will be explained. The first series of calculations are used to determine the Equation of State of the system, which is used to evaluate the classical conservation equations used in hydrodynamic predictions of detonation. The second type of calculations are computer experiments in which the model of this energetic molecular crystal is subjected to flyer plate impact. A shock wave then propagates through the crystal, with reaction occurring almost immediately behind the shock discontinuity. Macrocropic properties of the material behind the shock wave are then compared with the hydrodynamic predictions. Agreement between the computer experiment and hydrodynamic predictions is excellent. The reaction mechanism for the detonation involves a pressure-induced atomization of the reactants behind the detonation wave rather than excitation of molecular vibrations. The significance of this observation is discussed. Monday , February 26 1996 5:00 pm Room 206, Science & Tech. I -------------------------------------------------------------------