Spatiotemporal behavior of void collapse in shocked solids.

Molecular dynamics simulations on a three-dimensional defective Lennard-Jones solid containing a void are performed in order to investigate detailed properties of hot spot generation. In addition to the temperature, I monitor the number of energetically colliding particles which characterizes the intensity of shock-enhanced chemistry. This quantity normalized by void volume is found to saturate for nanoscale voids and to be maximized after voids have completely collapsed. It makes an apparent comparison to the temperature which requires much larger void for the enhancement and becomes maximum during the early stage of the collapse. It is also found that the average velocity and the temperature of ejected molecules inside a cubic void are enhanced during the collapse because of the focusing of momentum and energy towards the centerline of a void.