Influence of ion pseudopotential on the electronic shell structure of metal clusters

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Abstract
Electronic shell and supershell structures in spherical multiple-shell and liquidlike clusters, taking into account the electron-ion interaction through usual empty-core pseudopotentials, have been investigated for trivalent and alkali species and compared with the conventional jellium model. In the case of multiple-shell structures we find that the jelliumlike electronic shell structure is clearly developed, in spite of the strong inhomogeneities in the ion density. The supershell pattern is, however, strongly dependent on the geometrical structure and pseudopotential parametrization. In the case of a homogeneous ionic distribution, the overall effect of the non-Coulombic behavior of the pseudopotential at short range is reflected through a softness increase of the effective electronic potential, acting as a diffuse jellium. Results about the shell and supershell structures are in better agreement with experiments, as compared to the standard jellium-model predictions. This effective surface softness, arising only from the finite size of the ionic cores, could also partially correct the present disagreement between experiment and jellium calculations with regard to the cluster polarizabilities and surface plasmon frequencies.