Calculated relaxation of the outmost layers of Pb films as a function of the layer thickness. and are the change in layer spacing between the first and second layers and between the second and third layers, respectively. is the layer spacing along the  direction in bulk Pb.
(a) adsorption sites on Pb (111). Here, the sites are denoted by HH(1,2,3), FH(1,2,3), T(1,2,3), and B(1,2,3). HH, FH, T, and B, respectively, to represent adsorption at the hcp hollow, fcc hollow, top, and bridge sites. Numbers 1, 2, and 3 denote the orientation along the (i.e., ), (i.e., ), and (i.e., ) directions, respectively. The molecule in a stable site is represented by a red dimer; otherwise, it is represented by a blue dimer. [(b), (c), and (d)] The three relaxed structures at the HH site. Red and gray atoms represent O and Pb. There is a Pb atom in the second layer below the HH site to make it distinct from the FH site.
(a) Calculated PDOS of the system at the HH1 site. Fermi energy (dotted line) is set to be the energy zero. [(b) and (c)] Isosurface plots of the charge density at the two deep hybridized energy states after adsorption at the HH1 site. Red and gray atoms are O and Pb, respectively.
(a) Charge-density difference for the adsorption on a 7 ML Pb film. Red and gray atoms represent O and surface Pb. Regions of electrons accumulation/depletion are displayed in blue/yellow, respectively, and the isosurface value is . (b) Line density plot along the direction. The top of the Pb surface is set to reference zero. The red line separates the positive and negative charges at the interface.
The adsorption energy calculated with both PW91 and rPBE functional form, and the effective binding energy as a function of the film thickness. The red line plot and the labels to the right of the figure are for the charge transfer at the interface.
The adsorption energy , bond length denoted in Figs. 2(b)–2(d), and atomic height of at the HH sites of a 7 ML Pb(111) film, in units of eV and Å, respectively.
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