Transition from atomistic to macroscopic cluster stopping in Au

Based on large-scale molecular dynamics simulations of Au cluster impacts on a Au surface, we have recently reported that the transition to macroscopic crater volume scaling behavior occurs between 1000 and 100,000 Au atoms at impact velocities comparable to typical meteoroid velocities [J. Samela, K. Nordlund, Atomistic simulation of the transition from atomistic to macroscopic cratering, Phys. Rev. Lett. 101 (2008) 027601]. Now we have analyzed the conditions that lead to this transition in more detail. The main mechanisms of this change is the emergence of the transient high-density region which can store two thirds of the impact energy. This mechanism becomes the dominant cratering mechanisms gradually when the impactor size increases.