Interpolation scheme for the cohesive energies for the lanthanides and actinides

An interpolation scheme for the binding energies is shown to give a good account for the cohesive energies of the rare-earth metals. From this the divalent nature of europium and ytterbium can be concluded. The same method is applied to the actinide elements. The observed deviations from experiment are interpreted in terms of itinerant $5f$ states. Further, a divalent metallic character of the heavier actinide elements, starting with einsteinium, is predicted.