First-principles evaluation of the surface barrier for a Kohn-Sham electron at a metal surface

The popular local-density approximation neglects long-range correlations which, in the presence of the rapid rate of change of the electron density at the surface, lead to observable effects. We evaluate the exchange-correlation potential Vxc for the electron gas-vacuum interface from the knowledge of the electron self-energy Σxc in the GW approximation. The electron-electron correlations built into Σxc automatically produce an imagelike surface barrier. Our result for Vxc is the basis of a nonlocal density-functional calculation of the electronic structure of Al(100) which yields a Rydberg series of image states from first principles.