Diffusion in a strongly correlated anisotropic overlayer

We study the collective diffusion in chain structures on anisotropic substr ates like (1 1 2)bcc and (1 1 0)fcc surfaces with deep troughs in the subst rate potential corrugation. These chain structures are aligned normal to th e troughs and can move only along the troughs. In a combination of theoreti cal arguments and of numerical simulations, we study the mass transport in these anisotropic systems. We find that a mechanism similar to soliton diff usion, instead of single particle diffusion, is still effective at temperat ures well above the melting temperature of the ordered chain structures. Th is mechanism is directly correlated with the ordered phases that appear at much lower temperatures. As a consequence. also the influence of frozen dis order is still visible above the melting temperature. Theoretically we pred ict a strong dependence of the pre-exponential factor and weak dependence o f the activation energy on the concentration of frozen surface defects. The se predictions are confirmed by the simulations. (C) 2001 Published by Else vier Science B.V.