The diffusivity of Ga and Al adatoms on the (2x4) reconstructed GaAs(001)
surface are evaluated using detailed ab initio total energy calculations of the
potential energy surface together with transition state theory. A strong
diffusion anisotropy is found, with the direction of fastest diffusion being
parallel to the surface As-dimer orientation. In contrast to previous
calculations we identify a short--bridge position between the two As atoms of a
surface dimer as the adsorption site for Al and Ga adatoms.Comment: 4 pages, 1 figures, to appear in "The Physics of Semiconductors
