Molecular-dynamics study of detonation .1. A comparison with hydrodynamic predictions

We have compared the predictions of hydrodynamic theory for the properties of an unsupported detonation with the results of a molecular dynamics simulation of such a phenomenon. The model of an energetic crystal consists of heteronuclear diatomic molecules that require energy to break the molecular bonds (at ambient pressure); substantial energy is then released upon association of the products to form homonuclear diatomic molecules. The equation of state used in the hydrodynamic theory is determined from two-dimensional molecular dynamics simulations of this model at various equilibrium conditions corresponding to volumes and temperatures appropriate to the detonation. The Chapman-Jouguet conditions of detonation were thus determined. The properties of the detonation were subsequently measured directly from two-dimensional molecular dynamics simulations of the crystal model subjected to shock initiation. The agreement between the hydrodynamic predictions and the measured properties is good. Deviations from exact agreement are attributed to slight differences in material composition in the detonation simulation compared to that of the equation of state calculations. The critical property for sustained detonation using this model appears to be the attainment of the Chapman-Jouguet density.