COMBINED EFFECT OF HYBRIDIZATION AND EXCHANGE COULOMB INTERACTION ON MAGNETIC-ORDERING IN CORRELATED-F-ELECTRON CERIUM SYSTEMS

The model Hamiltonian describing the partially delocalized f-electron system has been generalized to include both hybridization and band-f e xchange Coulomb interaction. A method has been developed to calculate the parameters appearing in such a model Hamiltonian from first princi ples. This enables us to calculate f-electron-based electronic and mag netic phenomena of pertinent materials on a quantitative basis. Calcul ations have been done for cerium monopnictides and monochalcogenides. Results are in agreement with experiment on various unusual behaviors of these materials, such as anomalous crystal-field splitting and anis otropic magnetic ordering, all of which are caused by the interactions between f electrons and band electrons. In contrast to the earlier ve rsion of this theory that included only hybridization effects and prod uced range parameters (two-ion ''exchange'' coupling) that failed by a n order of magnitude in matching the phenomenologically determined par ameters which provide agreement with experiment, the present first-pri nciples theory calculations which also include band-f Coulomb exchange provide excellent agreement with the phenomenologically required magn itude.