Bound states in screened and bare Coulomb potentials: A nonorthogonal CI-Based route to effective Hamiltonians for two-electron systems

One- and two-electron bound states in screened and bare Coulomb potentials are calculated by adopting a discretized multiconfiguration generator coord inate (GC) method which leads to an iterative nonorthogonal configuration i nteraction procedure with the optimization of GCs. The GCs are optimized ei ther by the method of simulated annealing or by a genetic algorithm. Critic al scanning lengths for which bound states disappear in one-electron atoms are computed. A noninteracting model Hamiltonian for a two-electron atom ba sed on the idea of screened Coulomb interaction is proposed and used for ca lculating electric dipole polarizability and establishing the threshold val ue of z for the appearance of autoionizing ground state of two-electron sys tems. (C) 1999 John Wiley & Sons, Inc.