Electronic excitations in 3d transition metals.

Abstract

We calculate the direct and inverse photoemission spectra of 3d transition metals with fcc or bcc structure. The dynamics of the d electrons is described by an extended Hubbard model including five canonical d bands in the one-particle operator ${\mathit{H}}_{0}$ and all relevant on-site Coulomb and exchange matrix elements in the interaction Hamiltonian ${\mathit{H}}_{1}$. For the ground state a quantum-chemical ansatz is made taking local spin and density correlations into account. The retarded Green's functions of the d electrons are evaluated by using the projection technique of Mori and Zwanzig. Thereby the dynamics of the additional particle is projected onto local spin and density excitations in analogy to the ground-state calculation and treated exactly within that restricted operator space. In the case of Ni the correct satellite position and a reasonable reduction factor of the bandwidth are obtained by using an experimentally determined parameter set. The numerical calculations for our model Hamiltonian also predict multiplet structures in the photoemission spectra of Co and Fe.