Efficiency of Energy Localization in Hotspot Formation for Complex Pore Collapse Mechanisms

Previous works in both atomistic and continuum modeling of shock induced pore collapse have shown that the collapse mechanisms at lower shock speeds, dominated by plastic deformation, are more efficient at localizing temperature than the hydrodynamic collapse invoked at stronger shocks. Yet, these provide significantly lower absolute temperatures due to the low shock pressures and velocities involved. Highly anisotropic crystal structures are known to leads to a variety of complex collapse mechanisms at different shock strengths and pore sizes. However, these mechanisms are not well characterized with respect to one another. Therefore, we run all-atom molecular dynamics simulations of shock induced pore collapse in an anisotropic molecular crystal with a strong hydrogen bonding network, using four different impact velocities and pore sizes that range across an order of magnitude. We find that a complex, lateral collapse mechanism resembling atomic scale extrusion leads to extremely efficient hotspot formation mechanism as low shock pressure. However, the strength of the hydrogen bonding network is shown to greatly limit the ability to produce high temperature hotspots at high shock strengths.