The 5-parameter Morse potential (5-MP) of the interaction between Cl atom and Ag surface has been constructed. The adsorption and diffusion of Cl on Ag low index-surfaces were investigated with 5-MP in detail. All critical characteristics of the system have been obtained, such as adsorption site, adsorption geometry, binding energy, eigenvalues for vibration, etc. The calculated results show that Cl atom is located in the fourfold hollow site of the intact Ag(100) surface. Although quasi-3-fold site and long-bridge site is a stable adsorption site on Ag(110) surface for the first and second period atoms, the fourfold-hollow becomes the most stable adsorption site for Cl on Ag(110) and Cl atom tends to occupy 3-fold site on Ag(111) surface. For the Cl-Ag surface adsorption system, the surface binding energy of Cl atom is relevant to the coarse degree of cluster surface with the binding energy ordered as (111)＜(100)＜(110).

Key words: Cl-Ag system, 5-MP, surface adsorption, surface vibration