First-principles study of surface electronic structures of half- and full-monolayer Na on a Ta(110) surface

We investigated the electronic structures for half-monolayer (HML) and full -monolayer (FML) coverages Na on Ta(110) surfaces by employing the all-elec tron full-potential linearized augmented plane wave (FLAPW) method. We find that the calculated work function is increased from 2.27 eV for the HML Na coverage to 3.51 eV for the FML one. The calculated density of states and charge density contours at the surface region show a transition from an ion ic to a metallic character as the Na coverage increases. The mechanism for the work function change and the metallic transition are discussed in relat ion with adlayer-substrate band hybridization.