Local Density Approach to Surfaces and Adsorbed Layers

Abstract

We show that the local density problem for the thin film geometry can be solved with high accuracy by employing our all-electron full-potential linearized augmented-plane-wave (FLAPW) method. This is achieved by removing all shape approximations in the charge density and the potential and by using a highly flexible variational basis set. Its utility even for treating molecules on surfaces is demonstrated for the severe test case of the (nearly) free O₂ molecule where the FLAPW method is found to be at least as accurate as state-of-the art localized-basis molecular methods. The high accuracy and precision of the FLAPW approach for metallic surfaces is shown by our finding that for the interpretation of surface sensitive photoemission measurements of the Al-2p core levels both a surface induced core level shift of 120 meV to reduced binding energies and a 38 meV crystal field splitting are important. Based on all-electron local density calculations we explain the lowering of the work function of a transition metal surface [W(001)] upon deposition of a Cs over-layer by a multiple dipole formation. Finally, we demonstrate for a graphite monolayer that local density total energies give excellent descriptions of equilibrium geometries and discuss the overestimation of local-density cohesive energies due to an incomplete treatment of correlation effects in the free atom.