Ordered phases of potassium on Pt{111}: Experiment and theory

Abstract

Using low-energy electron diffraction structural analysis and first-principles calculations based on the local-density approximation we have investigated the $(\sqrt{3}\ifmmode\times\else\texttimes\fi{}\sqrt{3})R30\ifmmode^\circ\else\textdegree\fi{}$ K and $(2\ifmmode\times\else\texttimes\fi{}2)$ K overlayers on Pt{111}. The measured and calculated adsorption geometries agree quantitatively. In both phases the K adatoms occupy threefold symmetric hcp hollow sites, the preference for the hcp site over the fcc site being a consequence of the polarization of the surface Pt $d$ electrons. We have not found any indication of K incorporation into the Pt{111} surface, as has been recently suggested.