THE GROUND STATE OF ATOMIC TWO-ELECTRON SYSTEMS IN THE INDEPENDENT PARTICLE MODEL

Scaled variational functions of the form (Phi sub alpha(k)) = e exp. -(Z-1+e exp. -(alpha(kr)))kr, where Z is the nuclear charge and alpha is a parameter, and (Phi sub beta(alpha)(k)) = exp. -(beta + e exp -(alpha(kr)))kr, where both alpha and beta are parameters, are used for the description of the ground state of atomic two-electron systems in the independent particle model. The scale factor k has been introduced in order to satisfy the virial theorem. Apart from the energy, a number of one-electron expectation values have been calculated and the results are compared with those obtained from other variational functions. The function (Phi sub alpha(k)) yields already a good approximation to the Hartree-Fock solution whereas with the function (Phi sub beta(alpha)(k)) the Hartree-Fock results are practically reproduced. (Author)