Hartree–Fock stability and symmetry breaking: oxygen doubly negative ion

The Hartree–Fock stability problem, its relationship to the broken symmetry solutions, and the implications for a molecular nuclear framework distortion are briefly reviewed. The case where no nuclear framework distortion is possible is studied for the oxygen doubly negative ion, using an abinitio Slater-type orbital analytical approach, in order to illustrate other possible implications of the symmetry breaking in the independent particle models. It is shown that the existing pure singlet broken symmetry solutions for this ten electron ion, which were obtained earlier by adhoc procedures, follows systematically and straightforwardly from the HF stability problem for the corresponding symmetry adapted solution which shows a strong singlet instability. The chemical and physical implications of this type of symmetry breaking are briefly discussed.