Simulation of chemical reaction initiation through high velocity collisions of NO clusters with a surface

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Abstract
Some computational results have been obtained for a system of diatomic molecules clustered together and driven to impact on a surface at sufficient energy to induce an observable quantity of chemical reactions. The diatomic molecules were modeled to be energetically similar to nitric oxide, NO, which is a detonable material when in the condensed phase. The system was intended to simulate an experiment devised to examine the initiation phase of a detonation of liquid NO stimulated by impact with a high‐speed flyer plate. Classical trajectories were computed for six different cluster sizes, from 4 molecules to 50, and the clusters were directed into a wall at five different impact speeds ranging from 3.0 to 11.8 km s−1. The interatomic forces used for the computations were based on a modification of an empirical potential suggested by Tersoff. The characteristics of the products (O2, N2, NO, and N and O atoms) are examined, as well as the dynamic features of the collisions of the clusters with the wall. The conditions of the cluster impacts produced atom densities that were nearly triple the initial density of the clusters. The reactions in the n=50 cluster are complete in less than 300 fs. These conditions are unusual for studies of chemical reactions so that the many‐body effects are expected to be important. They are conditions experienced in the initiation of explosive detonations.