Displacement distribution and atomic jump direction in diffusion of Ir atoms on the Ir(001) surface

On the Ir001 surface an Ir adatom is surprisingly found to jump along the 〈001〉 direction instead of along the smoother closely packed 〈110〉 atomic channel of the substrate, probably by an atomic exchange mechanism. The sites visited by one diffusing adatom therefore form a c (22) net of the substrate lattice. The displacement distributions derived are consistent with those expected from a discrete random walk with the atomic jump length of the nearest-neighbor distance of the c (22) net.