AB-INITIO CALCULATIONS OF COULOMB U-PARAMETERS FOR TRANSITION-METAL IMPURITIES

We present ab initio calculations for the Coulomb U parameter of all t ransition-metal impurities in Rb. The U parameter increases in each ro w by filling up the d shell and decreases with increasing row number. In addition we find a strong configuration dependence, with the Hubbar d U of 3d impurities being about 30% larger for the divalent configura tion than for the monovalent one.