SIMULATION OF CHEMICAL-REACTION INITIATION THROUGH HIGH-VELOCITY COLLISIONS OF NO CLUSTERS WITH A SURFACE

Some computational results have been obtained for a system of diatomic molecules clustered together and driven to impact on a surface at suf ficient energy to induce an observable quantity of chemical reactions. The diatomic molecules were modeled to be energetically similar to ni tric oxide, NO, which is a detonable material when in the condensed ph ase. The system was intended to simulate an experiment devised to exam ine the initiation phase of a detonation of liquid NO stimulated by im pact with a high-speed flyer plate. Classical trajectories were comput ed for six different cluster sizes, from 4 molecules to 50, and the cl usters were directed into a wall at five different impact speeds rangi ng from 3.0 to 11.8 km s(-1). The interatomic forces used for the comp utations were based on a modification of an empirical potential sugges ted by Tersoff. The characteristics of the products (O-2, N-2, NO, and N and O atoms) are examined, as well as the dynamic features of the c ollisions of the clusters with the wall. The conditions of the cluster impacts produced atom densities that were nearly triple the initial d ensity of the clusters. The reactions in the n=50 cluster are complete in less than 300 fs. These conditions are unusual for studies of chem ical reactions so that the many-body effects are expected to be import ant. They are conditions experienced in the initiation of explosive de tonations. (C) 1996 American Institute of Physics.