STABLE DEFORMATIONS IN LARGE METALLIC CLUSTERS

Only a relatively small number of metallic clusters exhibit a stable spherical shape. We show that the majority of such clusters tend to acquire a deformed shape, in order to minimize the fluctuating part of the total energy, due to the bunching of the single particle electronic levels in a confined geometry. We have found also that there is a large number of low lying shape isomers. Often the deformation energy surface develops rather wide shallow pockets and such clusters are particularly easy to deform. As a function of the electron number the cluster ground state deformations and isomer energies show some remarkable regularities.