  Shock wave interactions with defects, such as pores, are known to play a key
role in the chemical initiation of energetic materials. The shock response of
hexanitrostilbene is studied through a combination of large scale reactive
molecular dynamics and mesoscale hydrodynamic simulations. In order to extend
our simulation capability at the mesoscale to include weak shock conditions (<
6 GPa), atomistic simulations of pore collapse are used to define a strain rate
dependent strength model. Comparing these simulation methods allows us to
impose physically-reasonable constraints on the mesoscale model parameters. In
doing so, we have been able to study shock waves interacting with pores as a
function of this viscoplastic material response. We find that the pore collapse
behavior of weak shocks is characteristically different to that of strong
shocks.
