Chemisorption of atomic chlorine on metal surfaces and the interpretation of the induced work function changes

The interaction of Cl on different metal surfaces has been studied by density functional theory. The surface is represented by periodic slab models. It is shown that the change on the surface work function induced by the presence of the adsorbed halide can be either positive or negative, depending on the surface metal. While this has already been pointed out for some particular cases such as Cl on Cu(0 0 1) or N on W(1 0 0), we show that this effect may also appear in the case of having the same adsorbate on different metal surfaces. Therefore, one may conclude that the use of the work function change to extract information about the net charge on the adsorbate should be regarded with extreme caution.