1ST-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 V(xc) for the electron gas-vacuum interface from the knowledge of the electron self-energy SIGMA(xc) in the GW approximation. The electron-electron correlations built into SIGMA(xc) automatically produce an imagelike surface barrier. Our result for V(xc) 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.