U. Kleinekathofer et al., BOUNDARY-CONDITION-DETERMINED WAVE-FUNCTION FOR THE GROUND-STATE OF HELIUM AND ISOELECTRONIC IONS, Physical review. A, 54(4), 1996, pp. 2840-2849
A simple nonvariational wave function for two electron atoms is descri
bed. The radial part is derived from the asymptotic one-electron wave
functions that are modified to account for the proper core boundary co
nditions. The electron-electron correlation is described by an ansatz
which has the correct behavior for r(12)-->0 and r(12)-->infinity. The
additional parameter in this ansatz is calculated from a perturbation
calculation. This wave function yields ground-state energies for the
heliumlike atoms with Z=1 (H-) to 10 (Ne8+) within 0.0021-0.0068E(h) o
f the exact energies, which is significantly better than obtained with
previous models. We also calculated [r(2n)] and multipolar polarizabi
lities and performed other tests on this wave function.