Correlation mechanism of f-electron delocalization

The mechanism off-electron delocalization is investigated within the multiorbital Anderson lattice model by means of diagrammatic perturbation theory from the atomic limit. The derived equations couple the intraatomic transition energies, their spectral weights, and the population numbers of the many-electron states. A self-consistent solution for praseodymium metal shows that the delocalization can be caused by external pressure via a resonant mixing off and conduction electrons in the vicinity of the the Fermi surface. We also find the following. (1) An increase of mixing leads to a decrease of the physical values of the Hubbard interactions U*; the reduction, however, is small. (2) The initial Hubbard U is split by renormalization into a set of different physical values of U*(i,j). (3) The gain in cohesive energy together with the f-sum rule cause a transfer of spectral weight, which is decisive for the delocalization off electrons. (4) The correlated fermionic quasiparticles have their bandwidth slightly reduced compared to those obtained using the Kohn-Sham equation.