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) calculations. Both cation and anion formations were found to strengthen the clusters due to the bonding character of their HOMO and antibonding nature of LUMO. The twin formation with bond lengths significantly smaller than those in the bulk palladium and in the corresponding neutral particles was found to 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 intermetallic interaction in charged clusters, both excess and deficit of electron density were found to cause the significant broadness of the d-zone. (C) 2000 Elsevier Science B.V. All rights reserved.