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 2 0, including the ionic structure of the clusters. The validity of a collect ive model for the static response of small systems is demonstrated. Our den sity 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 th e calculated polarizabilities. in better agreement with experiment. We rela te remaining differences in the magnitude of the theoretical and experiment al polarizabilities to the finite temperature present in the experiments.