Simulation of cluster impacts on metallic surfaces

Energy, number-density, and confinement-time properties of 1-keV/atom ${\mathrm{Al}}_{32}$ and ${\mathrm{Al}}_{63}$ cluster impacts on Al and Au targets have been investigated by molecular-dynamics simulation. Inertial confinement of the incoming clusters leads to number-density increases of ∼2 for very short time periods (<20 fs) in the primary impact zone. Simultaneous and near-simultaneous multiple collisions occasionally increase the potential energy of a particle to more than twice that allowed in isolated two-body collisions. Up to 12% of the kinetic energy of the incoming cluster is transferred to atoms which eject early in the collision cascade.