On a series of face-centered cubic (111) surfaces modelled by the embedded atom method, adatom diffusion mechanisms were studied systematically by molecular dynamics. On most surfaces, as expected, the diffusion mechanism was only hopping. For some other surfaces, however, it was found that the exchange mechanism was possible besides the well-known hopping mechanism. More interesting was that the hexagonal close-packed and face-centered cubic sites were now different for adatom diffusion: the exchange diffusion process only occurred between the hexagonal close-packed sites.

Mechanisms for Adatoms Diffusing on Metal FCC(111) Surfaces. Zhuang, J., Liu, L., Ning, X., Li, Y.: Surface Science, 2000, 465[3], 243-8