Coexisting superstructures of iodobenzene on Cu(1 1 1) near saturation coverage

Low-temperature scanning tunnelling microscopy reveals seven coexisting structures of iodobenzene (IC6H5) adsorbed on Cu(1 1 1) at ≈55 K. Only the least dense structure reflects the threefold symmetry of the surface. The other structures show p2-symmetry. In the densest structure molecules adsorb with their π system perpendicular to the surface. We identify as a common driving force for ordering the tendency of the phenyl rings (C6H5) to encapsulate the iodine.