Image-potential states at metal surfaces

Density-functional theory is applied to calculate image-potential states at metal surfaces with different electron densities (r s =2, 3, 4, 5, 6). The surface potential, obtained from a self-consistent quantum mechanical calculation based on the jellium model, yields the correct long-range image potential, since a non-local exchange-correlation energy functional is used. The many-body effects lead to drastic changes in the energies of the Rydberg states n=1, 2, both at high and at low electron densities.