By using the plane-wave pseudopotential method, density-functional theory calculations were made of the stability of steps and self-diffusion processes on Ag(100). The calculated step formation energies showed that the {111}-faceted step was more stable than the {110}-faceted step. It was found, in agreement with experimental data, that the equilibrium island shape should be octagonal (very close to square), with predominantly {111}-faceted steps. In the case of the (100) surfaces of face-centered cubic metals, atomic migration occurred via hopping or exchange processes. Adatoms on Ag(100) diffused across flat surfaces mainly by hopping. Adatoms which approached the close-packed {111}-faceted step edges descended from the upper terrace to the lower level via an atomic exchange which involved an energy barrier that was almost identical to the diffusion barrier on flat surface regions. Within the numerical accuracy (±0.05eV), there was no additional step-edge barrier to descent. This provided an explanation for experimental observations of smooth 2-dimensional growth during the homo-epitaxy of Ag(100). Experimental data for other face-centered cubic crystal surfaces indicated that the present result was generally true.

B.D.Yu, M.Scheffler: Physical Review B, 1997, 55[20], 13916-24