The adsorption of a molecular electron donor on Au(111) is characterized by the spontaneous formation of a superlattice of monomers spaced several nanometers apart. The coverage-dependent molecular pair distributions obtained from scanning tunneling microscopy data reveal an intermolecular long-range repulsive potential, which decreases as the inverse of the molecular separation. Density functional theory calculations show a charge accumulation in the molecules due to electron donation into the metal. Our results suggest that electrostatic repulsion between molecules persists on the surface of a metal.

We study the electronic mechanisms underlying the induction and propagation of chirality in achiral molecules deposited on surfaces. Combined scanning tunneling microscopy and ab~initio electronic structure calculations of Cu-phthalocyanines adsorbed on Ag(100) reveal the formation of chiral molecular orbitals in structurally undistorted molecules. This effect shows that chirality can be manifest exclusively at the electronic level due to asymmetric charge transfer between molecules and substrate. Single molecule chirality correlates with attractive van~der~Waals interactions, leading to the propagation of chirality at the supramolecular level. Ostwald ripening provides an efficient pathway for complete symmetry breaking and self-assembly of homochiral supramolecular layers.

Highly oriented polycrystalline ${\mathrm{Bi}}_2\mathrm{Ca}{\mathrm{Sr}}_2{\mathrm{Cu}}_2{\mathrm{O}}_{8+\delta }$ has been studied by x-ray photoemission spectroscopy (XPS) to determine the oxidation states of its constituents and the valence electronic structure. Core-level shifts indicate 3+ and 2+ as main oxidation states for Bi and Cu, respectively. The Ca and Sr core levels exhibit pronounced shifts to lower binding energy compared to the metals. The Ca lines show two main components, indicating either inequivalent sites or the presence of a different phase. The XPS and ultraviolet photoemission spectroscopy valence-band spectra show weak but reproducible metallic emission at the Fermi level ($E_F$) which we ascribe to states originating in the Bi-O planes. The main $\mathrm{Cu} d-\mathrm{O} p$ band is between 2 and 8 eV below $E_F$; this is about 1 eV lower than predicted by band-structure calculations. We argue that this is due to electronic correlations tending to increase the anisotropy in the ground-state charge distribution compared to that obtained in local-density-approximation calculations.