NONLOCAL ION POTENTIAL EFFECTS ON THE OPTICAL-RESPONSE OF LITHIUM CLUSTERS

We present a spherical symmetry model, containing explicitly nonlocal effects in the electron-ion interaction, to describe the electronic pr operties of lithium clusters. We assume either an optimized discrete i onic structure or a jellium structure. The model provides the nonlocal potential from which the random phase approximation with exact exchan ge is applied to calculate the optical response of Li clusters. The op tical response of Li-139(+) obtained within this model is in good agre ement with the measured giant dipole resonance. The same model is used to predict alkali-metal effective masses; the agreement with band str ucture calculations is emphasized.