DENSITY-FUNCTIONAL CALCULATION OF THE PHOTOABSORPTION SPECTRUM OF SIMPLE METAL-CLUSTERS - BEYOND THE LOCAL-DENSITY APPROXIMATION AND JELLIUM MODEL

The time-dependent density functional theory has been used to calculat e the photoabsorption spectrum of small alkali metal clusters, for whi ch comparison with experiments is possible. Most theoretical works hav e used firstly the local density approximation for exchange and correl ation effects and secondly the jellium model to simulate the ionic bac kground. In this paper we use the spherically averaged pseudopotential model to introduce geometric effects, and the weighted-density approx imation to account for non-local exchange-correlation effects. The inf luence of these effects is analysed for neutral and charged clusters o f alkali metals and considerably improved predictions are obtained.