THEORY OF THE OPTICAL AND MAGNETOOPTICAL SPECTRA OF CERIUM AND URANIUM-COMPOUNDS

The optical and magneto-optical (MO) spectra of cerium and uranium com pounds are investigated theoretically, using an energy-band approach i n combination with the linear-response formalism. The energy bands are obtained within the local-density approximation (LDA), as well as wit h its generalization in which explicit on-site Coulomb correlations ar e included (LDA+U). We find that for CeSb, CeSe, and CeTe the LDA+U ap proach gives an adequate description of the measured MO spectra. For C eSb we calculate a colossal MO Kerr rotation of about 60 degrees, whic h is in agreement with recent experiments. For the uranium compounds w e find that the LDA gives a good description of the MO spectra, if the 5f-electrons are sufficiently delocalized, as is illustrated by e.g., UAsSe. The MO spectra of the uranium monochalcogenides US, USe, and U Te pose a challenge to present-day correlated band theory: it is shown that for UTe, where the 5f-electrons are quasilocalized, the LDA+U ap proach gives a reasonable result. For US, and also for USe, a better d escription is obtained if, as a correction beyond the on-site Coulomb interaction U, a screened hole in the 5f-shell is taken into account.