Density-functional theory calculations of hopping rates of surface diffusion

Using density-functional theory we compute the energy barriers and attempt frequencies for surface diffusion of Ag on Ag(lll) with different lattice c onstants, and on an Ag adsorbate monolayer on Pt(lll). We find that the att empt frequency is of the order of 1 THz for all the systems studied. This i s in contrast to the so-called compensation effect, and to recent experimen tal studies. Our analysis suggests that the applicability of simple (common ly used) scaling laws for the determination of diffusion and growth paramet ers is often not valid. [S0163-1829(98)02444-8].