The adsorption Of X-2 (X = F, Cl and Br) on the perfect and defect graphite surfaces has been studied by means of effective cluster models together with density functional theory. It was disclosed that the X, molecule is inclined to dissociatively adsorb at the edge site of defect zigzag and armchair graphite surfaces. The dissociative adsorption and activation of X, at the armchair edge site is more favourable than that at the zigzag edge site, which is analogous to the adsorption behaviour of O-2 and N-2 reported in previous studies. Hence, these significantly suggest the detailed local edge carbon atoms arrangement, i.e., local geometrical environment, is able to exhibit an important role in the adsorption process. Furthermore, our present studies strongly suggest that the edge sites of defect graphite surface can be used as active sites for further chemical functionalization of graphite material for potential specific use. (c) 2005 Elsevier B.V. All rights reserved.