Static electric dipole polarizabilities of Na clusters

The static electric dipole polarizability of Na-N clusters with even N has been calculated in a collective, axially averaged and a three-dimensional, finite-field approach for 2 less than or equal to N less than or equal to 20, including the ionic structure of the clusters. The validity of a collective model for the static response of small systems is demonstrated. Our density functional calculations verify the treads and fine structure seen in a recent experiment. A pseudopotential that reproduces the experimental bulk bond length and atomic energy levels leads to a substantial increase in the calculated polarizabilities. in better agreement with experiment. We relate remaining differences in the magnitude of the theoretical and experimental polarizabilities to the finite temperature present in the experiments.