6S AND 4F IONIZED STATES OF THE LANTHANIDES CALCULATED BY NUMERICAL AND ANALYTICAL HARTREE-FOCK METHODS

The ground states, as well as the 6s and 4f ionized states of Ba, Cs, and lanthanide atoms from La to Lu, are calculated with the nonrelativistic numerical Hartree-Fock (HF) method and an analytical HF method with Gaussian-type functions (GTFs). It is shown that the nonrelativistic HF calculations well reproduce the experimental trends on the 6s and 4f electron ionizations, although the calculated 6s ionization potentials (IPs) are smaller and the calculated 4f IPs are larger than those given by experiment. The relativistic HF calculations with GTFs are also performed on some selected atoms. The 6s IPs given by the relativistic HF method are closer to experiment than those given by the nonrelativistic HF methods. The relativistic corrections make 4f IPs smaller than those of experiment. Since the correlation effects increase the IPs obtained by the HF calculations, the inclusion of the relativistic effects is indispensable in discussing IPs quantitatively. © 1995 The American Physical Society.