Mass-velocity and size-velocity distributions of ejecta cloud from shock-loaded tin surface using atomistic simulations

摘要

The mass (volume and areal densities) versus velocity as well as the sizeversus velocity distributions of a shock-induced cloud of particles areinvestigated using large scale molecular dynamics (MD) simulations. A generic3D tin crystal with a sinusoidal free surface roughness (single wavelength) isset in contact with vacuum and shock-loaded so that it melts directly on shock.At the reflection of the shock wave onto the perturbations of the free surface,2D sheets/jets of liquid metal are ejected. The simulations show that thedistributions may be described by an analytical model based on the propagationof a fragmentation zone, from the tip of the sheets to the free surface, withinwhich the kinetic energy of the atoms decreases as this zone comes closer tothe free surface on late times. As this kinetic energy drives (i) the(self-similar) expansion of the zone once it has broken away from the sheet and(ii) the average size of the particles which result from fragmentation in thezone, the ejected mass and the average size of the particles progressivelyincrease in the cloud as fragmentation occurs closer to the free surface.Though relative to nanometric scales, our model reproduces quantitativelyexperimental profiles and may help in their analysis.