Density-functional calculation of effective Coulomb interactions in metals

The effective Coulomb interaction between the localized electrons is calculated for Fe and Ce. It is found that a change in the number of 3d electrons in Fe is only screened to about 50% inside the Fe atom where the change was made, although perfect (100%) screening was expected for a metallic system like Fe. In Ce, on the other hand, the screening is very efficient. The difference is discussed. For Ce the calculated Coulomb interaction (6 eV) is in satisfactory agreement with experiment, while the result (6 eV) for Fe is surprising large.