A comparative study of finite nucleus models far low-lying states of few-electron high-Z atoms

We studied low-lying states of lithium-like and beryllium-like ions with Z = 80 and 100 less than or equal to Z less than or equal to 120 for differen tial effects due to variation of the nuclear charge density distribution. T he latter was represented by exponential, Gauss-type, and Fermi-type models , standardized to a common rms radius. Numerical Hartree-Fock and Dirac-Foc k-Coulomb calculations were performed. Changes in total energies due to the use of different models become increasingly important for high Z in relati vistic approaches. Different models may even lead to different sequences of atomic states, and thus energy differences between those states may vary b y an order of magnitude. (C) 2000 Elsevier Science B.V. All rights reserved .