ONE-ELECTRON ENERGY EIGENVALUES IN THE WEIGHTED-DENSITY APPROXIMATION TO EXCHANGE AND CORRELATION

We have calculated the one-electron energy eigenvalues (epsilon) and the ionization potentials (IP) of closed-shell Na(n) and K(n) clusters (n = 2, 8, 18, 20) within the framework of density functional theory, using the jellium model for the ionic background and the weighted-density approximation for exchange and correlation effects. When care is taken to construct the exchange-correlation potential with the proper asymptotic behaviour, then, first of all, IP is in very good agreement with experiment and, second, the ionization potential theorem (epsilon-HOMO = = - IP, where epsilon-HOMO is the eigenvalue of the highest occupied molecular orbital) is satisfied rather well. Problems with the two-electron case (dimer) are discussed.