Fig. 9: Schematic summary of dipole contributions.

a The per-atom dipole contributions from polarization (pink) and Smoluchowski smoothing (purple) are positive for Ag (grey) and Au (yellow) and decrease upon dimer formation. b The charge transfer (green) which is only present for Au adatoms is negative and likewise decreases when a dimer forms. c As a result, the total (absolute) per-atom dipole (black) of Ag adatoms decreases upon dimerization, while it remains constant for Au adatoms. Grey arrows represent the dipole moments of the dimers. Note that all arrow lengths only visualize trends without being quantitative.