Numerical simulations, of diffusion at crystal surfaces with various crystallographic orientations, demonstrated that diffusion was suppressed by the clustering process. If bound states of 2 adatoms did not exist at the surface, a quasi 2-dimensional Wigner crystal was formed; thus leading to a sharp decrease in the diffusion coefficient.

A.A.Berzin, A.I.Morosov, A.S.Sigov: Journal of Physics - Condensed Matter, 1997, 9[1], 33-41