Molecular dynamics simulations of energetic cluster impacts on Al, Cu and Au targets

Abstract

Energy, number-density, confinement-time and ejected-atom properties of cluster impacts on metallic surfaces for the Al_(63)−Al, Cu_(63)-Cu, Al_(32)-Au and Al_(63)-Au systems with incident cluster energies of 1 keV/atom have been investigated by molecular-dynamics simulation. Similar simulations have been carried out for composite clusters (38 Al atoms, 25 Au atoms) impacting gold targets. 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. Multiple collision processes occasionally increase the potential energy of a particle to several times the value allowed in isolated two-body collisions. However, these effects are not sufficient to explain recent cluster impact fusion data. Significant numbers of aluminum atoms are found to eject from incoming clusters upon impact with the target for the Al_(63)-Au, Al_(63)-Au and composite cluster-Au systems. Energy- and angle-distributions of sputtered target-atoms are consistent with relatively rapid amorphization of the single crystal targets used in the simulations.

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