Benchmark calculations for lanthanide atoms: Calibration ofab initioand density-functional methods

Relativistic ab initio pseudopotential and fully relativistic density-functional benchmark calculations have been carried out for the first to fourth ionization potentials as well as the df charge-transfer energies for the whole series of lanthanide atoms. It was found that the two approaches have essentially the same accuracy compared to the experimental values. In addition, it is shown that the present (nonrelativistic) density functionals work fairly well within an otherwise relativistic framework even for the rather compact $4f$ shells, correcting previous statements to the contrary.