The self-diffusion of dimers on several face-centered cubic (001) surfaces was investigated by using molecular-dynamics methods with embedded-atom potentials. As well as the conventional exchange mechanism, an exchange rotation mechanism was observed for the diffusion of dimers; in which place replacement induced by one adatom of the dimer occurred among several substrate atoms and led to a collective rotation around the other adatom. The frequency ratio of the occurrence of this mechanism, to that of the conventional one, could reach about 10% at high temperatures on one of the surfaces studied. A comparison with single-adatom diffusion showed that such rotation resulted from the complicated exchange mechanism of single adatom.

Exchange Rotation Mechanism for Dimer Diffusion on Metal FCC (001) Surfaces. J.Zhuang, Q.Liu, M.Zhuang, L.Liu, L.Zhao, Y.Li: Physical Review B, 2003, 68[11], 113401 (4pp)