Stabilized Spin-Polarized Jellium Model and Odd-Even Alternations in Jellium Metal Clusters

TL;DR

This paper extends the stabilized jellium model to include spin polarization, revealing that maximum spin compensation explains odd-even alternations in ionization potentials of metal clusters.

Contribution

The authors generalize the stabilized jellium model to account for spin polarization and positive background expansion, providing new insights into cluster energetics and ionization potential patterns.

Findings

Energy minimized at maximum spin compensation for clusters

Odd-electron clusters have one unpaired electron

MSC-rule explains ionization potential alternations

Abstract

In this paper, we have considered the mechanical stability of a jellium system in the presence of spin degrees of freedom and have generalized the stabilized jellium model, introduced by J. P. Perdew, H. Q. Tran, and E. D. Smith [Phys. Rev. B42, 11627 (1990)], to a spin-polarized case. By applying this generalization to metal clusters (Al, Ga, Li, Na, K, Cs), we gain additional insights about the odd-even alternations, seen in their ionization potentials. In this generalization, in addition to the electronic degrees of freedom, we allow the positive jellium background to expand as the clusters' polarization increases. In fact, our self-consistent calculations of the energetics of alkali metal clusters with spherical geometries, 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 even number of electrons, the energy minimization gives rise to complete compensation ($N_\uparrow=N_\downarrow$), and for clusters with odd number of electrons, only one electron remains uncompensated ($N_\uparrow-N_\downarrow=1$). It is this MSC-rule which gives rise to alternations in the ionization potentials. Aside from very few exceptions, the MSC-rule is also at work for other metal culsters (Al, Ga) of various sizes.