Non-Nearest-Neighbor Jumps in 2D Diffusion: Pd on W(110)

A variety of jumps has in the past been identified in diffusion of atoms on 1D channeled surfaces. To establish the jump processes important in diffusion on a 2D surface, the movement of individual Pd atoms has been examined on W(110). From the distribution of displacements of Pd at high temperatures, double jumps are found along the close-packed [Formula presented]. For the first time, sizable differences are also observed between the mean-square displacements along [Formula presented] and [Formula presented], which demonstrate unexpected contributions from jumps along [Formula presented], but not along [Formula presented]. These jumps proceed over activation barriers higher than for single jumps, under conditions predicted from previous work with Pd on the channeled W(211).