We have explored the deposition of size-selected AgN+ clusters (N=50–200) onto the graphite surface (at room temperature) over the impact energy range of 250–2500 eV, via a combination of scanning tunneling microscopy experiments and molecular dynamics simulations. We show that the clusters are pinned to the surface when the impact energy exceeds a critical value, which is proportional to the cluster size, N, via the formation of a point defect at the impact site. This prevents lateral diffusion of the clusters even at room temperature.

We have investigated the implantation of Ag N ͑N 20 200͒ clusters into a graphite substrate over the range of energies ͑E͒ 0.75 6 keV using molecular dynamics simulations. We find that after implantation the silver clusters remain coherent, albeit amorphous, and rest at the bottom of an open tunnel in the graphite created by the impact. It is found that the implantation depth of the clusters varies linearly as E͞N 2͞3 . We conclude that the cluster is decelerated by a constant force proportional to its cross-sectional area. We also identify a threshold energy for surface penetration associated with elastic compression of the graphite substrate.

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It is shown that neural networks can be used to fit a two-element many-body potential function. The system chosen is the C-H combination for which a many-body potential formulation due to Brenner exists. Comparison between this potential and the neural network indicates good agreement with both structure and energetics of the small C-H clusters and bulk carbon. However, because of the networks complicated structure, molecular dynamics simulations run at about a factor of 60-80% slower than with the Brenner many-body formalism.

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