Diffusion of a small two-dimensional symmetrical cluster Pd-7 on Pd(111) surface has been studied using canonical ensemble molecular dynamics (NVT-MD) with a many-body potential derived from first-principles calculations in bulk Pd. The results of the simulations performed at 800 K show several cluster diffusion events. Such events occur, mostly preserving the symmetrical shape. Nevertheless, our simulations indicate that distortion events do occur in a short time interval. During this time interval, more frequent diffusion events occur, with subsequent recomposition of the original shape of the cluster. These intermediate distorted states are short-lived and, therefore, would probably not be seen in the experiments. The migration mechanism is mainly row gliding for the compact symmetrical cluster, while for the distorted form the dominant process is a combination of single atom moves and edge gliding. (C) 2000 Elsevier Science B.V. All rights reserved.45241699239246