A Quantum-Chemical Study of the Adsorption of Pb Atoms on Au(111)

The interaction of lead atoms with a gold surface based on the cluster model of a metal surface has been investigated by the density-functional-theory (DFT) method. Geometrical and energy characteristics of these interactions have been evaluated. The adsorbed lead atom formed a strong chemical bond with gold-surface atoms. During the adsorption, there occurred a significant electron-density transfer from lead to gold. At the adsorption of a few lead atoms, flat lead nuclei tending to form a hexagonal structure were formed. The energy of adsorption of each subsequent lead atom depended insignificantly on the number of adsorbed atoms. The average effective lead atomic charge decreased with the increase of the lead quantity on the surface. The contribution of lead–lead interaction increased along with the increase in the number of lead atoms on the surface. Starting with intermediate occupancies, the contribution of lead–lead interaction to the submonolayer formation energy becomes significant. The emergence of adsorbed lead atoms on the gold surface increased the highest-occupied-molecular-orbital (HOMO) energy. This entails a decrease of the electronic work function upon the modification of a gold surface by lead.