Valencies in actinides

The electronic structures of the actinide metals are calculated with the self-interaction corrected local-spin-density approximation. This scheme allows for a splitting of the 5f electron manifold into an integral number of localized electrons and a self-consistently determined number of band 5f electrons, which hybridize into the non-f derived conduction states. For Pu, Am, Cm, Bk, and Cf, the lowest energy state is obtained when a total of three electrons are available for band formation, while for Es and Fm an additional localized f-electron is energetically favourable, leaving only two electrons for band formation. For U and Np, localization is never favoured. The present ab initio calculations reproduce the trend in valency throughout the actinide series, and the valency itself is determined by the same rules of the f-states hybridization as in the rare earths.