Quantum chemical study of neutral and single charged palladium clusters

The extended Huckel (EH) method with an electrostatic two-body correction, has been used in order to determine the structures of small single charged Pd-n clusters with n = 2-13 and to compare them with the neutral ones. The results for Pd-2 and Pd-3 are compared with density functional (DFT) calcul ations. Both cation and anion formations were found to strengthen the clust ers due to the bonding character of their HOMO and antibonding nature of LU MO. The twin formation with bond lengths significantly smaller than those i n the bulk palladium and in the corresponding neutral particles was found t o be the preferential way of growth for anionic clusters; cationic clusters show a more complicated behavior. The promotion of occupation of Pd 5s AOs is suggested to be responsible for the formation of 3D structures, whereas the stability of the planar configurations is attributed to the appearance of the vacancy in the valence 4d-shell. As a result of stronger intermetal lic interaction in charged clusters, both excess and deficit of electron de nsity were found to cause the significant broadness of the d-zone. (C) 2000 Elsevier Science B.V. All rights reserved.