A NEW METHOD FOR LARGE SCALE MOLECULAR DYNAMICS SIMULATIONS OF SHOCK-INDUCED EJECTA PRODUCTION

We propose a new method for modeling large scale shock-induced ejecta production using molecular dynamics (MD) simulations. A copper crystal with a sinusoidal surface finish representative of the roughness arising from a machine polishing is divided into a bulk and a surface part. The bulk part is simulated using the Hugoniostat technique, which allows a very large number of particles to reach a Hugoniot equilibrium state in a short physical time by the mean of a quasi-equilibrium MD simulation. The surface part is simulated with the NVE ensemble in order to account for the non-equilibrium character of the ejection process. With this method, the particles size distribution generated by a system with 125 million atoms is studied. Our MD results show that it exhibits a power law scaling in good agreement with the percolation theory. This theory suggests that the production of ejecta clusters is due to large scale fluctuations present near a critical point, where there is no dominant characteristic scale.