The low lying isomers of the copper nonamer cluster, Cu9

The lowest-lying isomers of the copper nonamer cluster, Cu 9 , are obtained from a genetic algorithm approach and density functional theory. Three isomers are found with relative energy differences of less than 0.07 eV, which makes the assignment of the global minimum structure difficult. The static electric dipole polarizabilities and dipole moments of these isomers are obtained from density functional theory employing a very extensive valence basis set together with an energy-consistent scalar relativistic pseudopotential for copper. The discrepancy between theoretically and experimentally obtained polarizabilities is discussed.