Optical and magneto-optical spectroscopy of uranium and plutonium compounds: recent theoretical progress

Abstract

First-principles calculations are reported which illustrate that, for those actinide compounds where the 5f electrons are sufficiently delocalized, energy band theory based upon the local spin-density approximation (LSDA) describes the optical and MO spectra reasonably well. Examples which we examine in detail are URhAl and UFe 2. The delocalized LSDA approach meets limitations for those actinide compounds, where the electrons in the correlated 5f shell are nearly localized. Just as in the case of lanthanide compounds having localized 4f electrons, a satisfactory description of the optical spectra could be obtained by using a generalization of the LSDA, in which explicitly f electron Coulomb correlations are taken into account (LSDA+ U approach). A third group consists of compounds in which the 5f electrons are neither fully delocalized nor localized, but have experimentally been classified as quasilocalized. The suitable theoretical approach to such compounds is yet to be resolved. We further consider the Pu monochalcogenides, the unusual physical properties of which were previously treated with different models, and discuss the optical spectrum of PuTe.