Geometry and core-level shifts of Li/GaAs(110) surface

We have performed total-energy density-functional calculations using ab initio pseudopotentials to determine the atomic structure of Li adsorbed on a GaAs(110) surface. From the calculated adsorption energies for different adsorption configurations of Li at 0.5 monolayer coverage, we have identified the most stable geometry showing 1 x 2 periodicity. This structure is found to be stabilized by charge transfer from the adatoms to the surface Ga dangling bonds. Based on this structure, we have calculated the core-level shifts of Ga 3d and As 3d. The calculated core-level shifts are in qualitative agreement with recent photoemission spectroscopy experiments, and provide a theoretical basis for the interpretation of the multiple components of core-level shifts.