Fig. 7: Charge density difference for dimer formation.

a, b Isosurface plots for isolated Ag and Au dimers (\(\Delta \rho ({{\bf{r}}})=\pm \)0.015 e Å⁻³, left) and for Ag and Au adatom dimer on the Ag(111) surface (\(\Delta \Delta \rho ({{\bf{r}}})=\pm \)0.015 e Å⁻³ and ± 0.007 e Å⁻³, centre, right). Charge accumulation is shown in red, depletion in blue. Vertical lines indicate the z height of the Ag surface atoms (grey, dashed) and of the adatom (solid grey (Ag) or orange (Au)). Adatom positions are indicated by filled grey and yellow circles. c, d Plots of the xy-integrated charge density difference ΔΔρ_xy(z) for the formation of Ag or Au dimers on the surface. The Δρ_xy(z) curves for single adatoms from Fig. 5 are shown in light grey. Surface and adatom positions are indicated by vertical lines.