Large-dimension configuration-interaction calculations of positron binding to the group-II atoms

The configuration-interaction (CI) method is applied to the calculation of the structures of a number of positron binding systems, including e⁺Be, e⁺Mg, e⁺Ca, and e⁺Sr. These calculations were carried out in orbital spaces containing about 200 electron and 200 positron orbitals up to ℓ=12. Despite the very large dimensions, the binding energy and annihilation rate converge slowly with ℓ, and the final values do contain an appreciable correction obtained by extrapolating the calculation to the ℓ→∞ limit. The binding energies were 0.00317 hartree for e⁺Be, 0.0170 hartree for e⁺Mg, 0.0189 hartree for e⁺Ca, and 0.0131 hartree for e⁺Sr.