A MODIFIED HUCKEL CALCULATION ON THE STRUCTURES AND IONIZATION-POTENTIALS OF AG CLUSTERS

The geometrical structures and ionization potentials of silver cluster s are studied by a modified Huckel theory including the variable Coulo mb integral resulting from different coordinate environments. The stab le atomic configurations of the Ag-n clusters are obtained by comparin g the energy of different structural isomers. The clusters with magic number atoms are found to adopt the near spherical host-like structure with higher symmetry, corresponding to the complete electronic shell. Based on those favorable structures the size dependent ionization pot entials of Ag-n are calculated up to 68 atoms by using this new develo ped modified Huckel theory. The theoretical values are in quite agreem ent with the experimental results as well as ab initio configuration i nteraction (CI) calculations. A transition from ''electronic order'' t o ''atomic order'' around n = 40 is proposed.