Comparative study of exchange-correlation effects on the electronic and optical properties of alkali-metal clusters

Ground-state properties of alkali-metal clusters are investigated within the framework of the jellium model from the standpoint of either the local-density approximation of the density-functional theory or the nonlocal Hartree-Fock theory. Accordingly, the optical response is calculated microscopically within the corresponding time-dependent theory. The present study deals with closed-shell systems with up to 200 delocalized electrons. A comparative investigation of various approximations is carried out. In spite of significantly different mean-field potentials, a consistent inclusion of polarization-type many-body effects leads to surprisingly similar theoretical predictions of the first moments of the oscillator strength distribution. This agreement is discussed in terms of sum-rule constraints. The remaining discrepancies with regard to the measured data originate from the jellium assumption which underlies our calculations.