Structures of chlorine on palladium (111)

ClK edge SEXAFS of the Pd(111)-(3×3) R30°-Cl surface reveals a Pd–Cl bond length 2.39 Å. Two previously unreported structures of chlorine on Pd(111) are identified, the (4×4) and a highly complicated surface with chlorine coverages of θ=0.57 and θ≤0.24, respectively, if the (3×3) R30° surface is assumed to be θ=0.33. The (4×4) structure is discussed in terms of a close packed hexagonal overlayer of chlorine on an unreconstructed metal surface and as a surface compound of palladium and chlorine. The highly complicated structure appears to comprise crystallites or islands of a palladium/chlorine compound and once formed is stable over a wide range of nominal chlorine coverages.