INFLUENCE OF NONLOCAL EXCHANGE-CORRELATION EFFECTS ON THE RESPONSE PROPERTIES OF SIMPLE METAL-CLUSTERS

Time-dependent density-functional theory has been used to study the photoabsorption spectrum of closed-shell sodium (Na-20, Na40) and potassium (K19-, K20, K91-, K92, K197-, K198) clusters within the spherical jellium model. We extend the treatment of exchange and correlation effects beyond the local-density approximation. The description of the exchange-correlation potential (especially its asymptotic part) and the local-field correction becomes improved in the weighted-density approximation that we use. Because of the larger number of bound states, we obtain an increased Landau damping. The position of the surface plasmon is given with errors of only 0.1 eV, and its fragmentation is explained due to the influence of particle-hole transitions. For the large negatively charged potassium clusters we predict the fragmentation of the surface plasmon due to its interference with the ionization threshold.