Weak Binding Potentials and Wetting Transitions

We present ab initio calculations of the adsorption potentials V(Z) of inert gases and hydrogen on the surfaces of various metals. The ratio of the adsorption well depth to that of the adsorbate pair potential is ∼ 3.5, 2, 1.5, 1, 0.9 and 0.9 for adsorption on Mg, Li, Na, K, Rb, and Cs, respectively, with some variation between gases (always smallest for Ne). When this ratio is small, a wetting transition occurs; we predict the wetting temperature T_w using a model of Cheng et al. Comparison is made with other calculations and with experiments.