Molecular Dynamics Study of Vacancy Cluster Formation Directly in Collision Cascades

In this work, the mechanisms of cascade collapse were investigated using molecular dynamics simulation method for copper. For this purpose, the simulations were carried out using the molecular dynamics code MOLDYCASK. Besides the density difference between the surrounding crystal and the molten zone, the atomic density difference is also fundamental to cascade collapse. Vacancy transport during the cascade thermal spike stage is determined by mean square displacement (MSD), the enhancement of mean square displacement due to an introduction of vacancies into the cascade volume. At the melting point of the material, mean square displacement is affected by the coefficient of vacancy diffusion, which is heavily influenced by initial vacancy density rather than deposited energy density.