Pair-correlation energy and successive ionization potentials of atoms He-Zn

The successive ionization potentials (IP’s) of atoms He–Zn are calculated using the relativistic and correlated local-density RCΞ method. The contribution of correlation energy to IP’s of these atoms are reported. It is found that these correlation contribution to IP’s are different for different IP’s of the same atom. It is also different for a given IP for different atoms. This behavior is qualitatively explained on the basis of the results of pair-correlation energy. A simple approximate expression to calculate the pair-correlation energy proposed earlier is discussed.