An analysis was made, of the in-channel diffusion of dimers and longer n-adatom chains on (110) surfaces, by using molecular dynamics simulations. This analysis included the self-diffusion of Au dimers and longer chains, on Au and Pt (110) surfaces, for both the (1 x 1) and (1 x 2) geometries. From the results, it was deduced that a novel (leap-frog) diffusion process predominated over concerted jumps on the missing-row reconstructed surface. Leap-frog events predominated at low temperatures, and caused a very different diffusion with respect to the (1 x 1) surface where, due to the geometry, this mechanism could not operate and thus n-adatom chains were hardly observed. The results indicated that the leap-frog mechanism for chain diffusion should be common on (110) missing-row surfaces; its occurrence being related more to the geometry of the surface than to the nature of the metal. The role played by out-of-channel trajectories in determining in-channel diffusion had already been noted for single-adatom diffusion on Au(110)-(1 x 2). In such a system, the trajectories were mainly of theoretical interest since they contributed to a small fraction of single jumps, to 25% of double jumps, and tended to overwhelm the rare long-jump events. In chain diffusion, however, leap-frogging became the dominant diffusion mechanism. Because of the energies involved, dimer leap-frog events were hardly experimentally detectable. On the other hand, the same type of event could also occur in longer chains and, in this case, the moving adatom spent a rather long average time above the chain. This made direct observation of the process possible.

Leapfrog Diffusion Mechanism for One-Dimensional Chains on Missing-Row Reconstructed Surfaces. F.Montalenti, R.Ferrando: Physical Review Letters, 1999, 82[7], 1498-501