Relativistic calculations of5pexcitation energies in the lanthanide metals

Abstract

A systematic investigation of $5p$ electron excitation energies in the lanthanide metals is reported. The renormalized atom method is used to construct crystal potentials, and excitation energies are derived from total band-energy differences. Calculations based on final states in which the $5p$ hole is screened by a conduction electron are in good agreement with x-ray photoemission measurements. Satellite levels associated with $4f$ electron screening in the final state are also considered. The change in $5p$ excitation energy accompanying a change in $4f$ occupancy is calculated for Ce, Sm, Eu, Tm, and Yb, elements which form fluctuating valence materials. These $5p$ replicate splittings are 3---4 eV, significantly smaller than cognate splittings for core electrons whose charge resides within the $4f$ shell. Screening energetics are examined via calculations for ionic final states. The relative effectiveness of conduction electron versus $4f$ electron screening is shown to be determined by the position of the ${4f}^{n+1}$ level in the $5p$ hole state.