On the ground state energies of first-row atoms and ions

Abstract

Truncation of the interelectron Coulomb potential at a minimum distance related to the energy has resulted in obtaining simple analytic forms for ground and excited state two-electron systems yielding good agreement for energies in comparison with other calculations. Extension of these methods using hydrogenic type wave functions has been accomplished for the Li-Ne isoelectron sequences. Ground state atom energies agree with “exact” nonrelativistic energies to within 0.1%, ranging from differences of - 0.00030 a.u. for Li and 0.00057 a.u. for Be up to a maximum difference of 0.05562 a.u. for F and 0.01339 a.u. for Ne. Tabulation of the energies of the ions for each sequence is given up to Z = 10. For Li to C the calculated ionization potentials agree with experiment to within 0.25 eV, but become progressively worse as the number of 2p electrons increases. For Ne the calculated ionization potential is only 15.835 eV rather than the experimental value of 21.55 eV. For ion energies the maximum differences from best other calculations are 0.25 a.u. for Ne+, decreasing to 0.02 a.u. or less for the 3- and 4-electron sequences, and tend to decrease with an increase in the degree of ionization.