Hybrid method for modeling epitaxial growth: Kinetic Monte Carlo plus molecular dynamics

We conduct molecular dynamics simulations of the collision of atomic clusters with a weakly attractive surface. We focus on an intermediate regime, between soft landing and fragmentation, where the cluster undergoes deformation on impact but remains largely intact and will either adhere to the surface (and possibly slide) or be reflected. We find that the outcome of the collision is determined by the Weber number We, i.e., the ratio of the kinetic energy to the adhesion energy, with a transition between adhesion and reflection occurring as We passes through unity. We also identify two distinct collision regimes: in one regime, the collision is largely elastic and deformation of the cluster is relatively small, but in the second regime, the deformation is large and the adhesion energy starts to depend on the kinetic energy. If the transition between these two regimes occurs at a similar kinetic energy to that of the transition between reflection and adhesion, then we find that the probability of adhesion for a cluster can be bimodal. In addition, we investigate the effects of the angle of incidence on adhesion and reflection. Finally, we compare our findings both with recent experimental results and with macroscopic theories of particle collisions.