STABILIZED SPIN-POLARIZED JELLIUM MODEL AND ODD-EVEN ALTERNATIONS IN JELLIUM METAL-CLUSTERS

In this paper, we have considered the mechanical stability of a jelliu m system in the presence of spin degrees of freedom and have generaliz ed the stabilized jellium model, introduced by Perdew ct al. [Phys. Re v. B 42, 11627 (1990)], to a spin-polarized case. By applying this gen eralization to metal clusters (Al, Ga, Li, Na, K, Cs), we gain additio nal insights about the odd-even alternations, seen in their ionization potentials. In this generalization, in addition to the electronic deg rees of freedom, we allow the positive jellium background to expand as the clusters' polarization increases. In fact, our self-consistent ca lculations of the energetics of alkali metal clusters with spherical g eometries, in the context of density functional theory and local spin density approximation, show that the energy of a cluster is minimized for a configuration with maximum spin compensation (MSC). That is, for clusters with an even number of electrons, the energy minimization gi ves rise to complete compensation (N-up arrow=N-down arrow), and for c lusters with an odd number of electrons, only one electron remains unc ompensated (N-up arrow-N-down arrow = 1). It is this MSC rule which gi ves rise to alternations in the ionization potentials. Aside from very few exceptions, the MSC rule is also at work for other metal clusters (Al, Ga) of various sizes. (C) 1998 American Institute of Physics.