COLLECTIVE SURFACE-DIFFUSION ON A TRIANGULAR LATTICE IN PRESENCE OF ORDERED PHASES

Diffusion is studied in a two-dimensional gas of triangular symmetry w ith repulsive interactions. The collective diffusion coefficient, D-c, is calculated as the ratio of the average jump rate and the zero-wave -vector static structure factor (Darken approximation). The dependence of D-c on coverage, theta, is studied in both the disordered and orde red regions of the phase diagram. It is shown that, around the coverag es of the perfect ordered phases (theta = 1/3 and 2/3), D-c changes of orders of magnitude in tiny B ranges. (C) 1998 Elsevier Science B.V. All rights reserved.