Atomic flows, coronas and cratering in Au, Si and SiO2

The traditional picture of ion irradiation effects in materials was that of a series of binary collisions. Since the 1980's it has, however, become clear that collective many-body effects such as heat spikes and flow of liquid matter can be important in dense metals. Now very recent atomistic simulations indicate that during MeV cluster ion bombardment, the irradiation effects start to resemble macroscopic phenomena such as the splashes and coronas observed when heavy objects fall on water. In this article, we review recent work showing that the craters formed during cluster impacts start to behave like macroscopic cratering beyond a certain impactor size. We also present new results which show that for cluster sizes of only around 100 atoms, not only dense metals, but also brittle materials like Si and SiO2 start to exhibit hydrodynamic-like behaviour of collective atom flow and corona formation.