Quasiparticle theory versus density-functional theory at a metal surface

We report a first-principles comparison between quasiparticle (QP) theory and density-functional theory (DFT) at a jellium surface. Once long-range Coulomb correlations---which are outside the local-density approximation---are incorporated into DFT through the exchange-correlation potential, the same yields wave functions and energy eigenvalues which are excellent approximations to their QP image-state counterparts. By contrast, our results for the electron self-energy near the surface do not support the use of local potentials for the description of excited-state damping.