Comment on “Self-diffusion and dynamic behavior of atoms at step edges on iridium surfaces”

Equilibrated two-dimensional Ir islands on Ir(111) exhibit longer $B$ steps (i.e., $〈110〉/{111}$ steps) than $A$ steps (i.e., $〈110〉/{100}$ steps). Accordingly, the $B$ steps have a lower step free energy than the $A$ ones, in contrast to the finding of Fu, Tzeng, and Tsong [Phys. Rev. B 54, 5932 (1996)]. With our results and a geometric model, several experimental results of Fu, Tzeng, and Tsong on the behavior of Ir clusters on Ir(111) can easily be understood.