Enhancement of Ag Cluster Mobility on Ag(111) Surface by clustering with Chlorine*

Chlorine is observed to accelerate the fragmentation of Ag nanostructures deposited on graphite. To understand the role of chlorine in the stability of Ag nanostructures, we have studied the formation and diffusion of Ag$_{n}$ and Ag$_{n}$Cl$_{m}$ (n= 1 to 4) clusters on Ag(111) surface, using density functional theory (DFT) with generalized gradient approximations (GGA) and the projector-augmented wave method. Our calculation shows that the formation energies and diffusion barriers of Ag$_{n}$ clusters are both lowered by clustering with chlorine when n=1, 3 and 4, indicating the enhancement of mass transport on Ag(111) surface. (AgCl)$_{n}$ clusters (n=1, 3 and 4) are good candidates for surface mass transport units. We have also studied a chloridized Ag$_{55}$ cluster and an Ag$_{55}$-Ag$_{55}$ neck structure. Chlorine is found to loosen the Ag$_{55}$ structure and weaken the binding between the Ag$_{55}$ bulbs in the neck structure.