AN ANALYTIC RELATIONSHIP BETWEEN SIZE AND IONIZATION-POTENTIAL OF TRANSITION-METAL CLUSTERS

Based on the effective coordination number (ECN) model, we have constr ucted an analytic expression for the size dependence of ionization pot entials (IPs) for transition-metal clusters. An approximate formula of the surface ratio as a function of cluster size for the close-packed structures has been fitted from the icosahedral-like structures. The I Ps of Co-n, Y-n, Nb-n, Ni-n are calculated and compared with experimen ts as well as with the prediction of the conducting spherical droplet (CSD) model. It is found that the present approach agrees with experim ent much better than the CSD model.