Relativistic configuration interaction using many-body techniques. Hyperfine interaction in Gd3+

A contribution is made to the development of fully relativistic configuration interaction using Brueckner-Goldstone many-body techniques. The theory is applied to the magnetic hyperfine interaction and the quadrupole hyperfine interaction in the Gd 3+ ion. For the general half-filled-shell case several formulae are given. In particular, the quadrupole analysis shows how this method provides a unique insight into the contributions to this complicated interaction. For the magnetic hyperfine interaction the authors made a detailed comparison with results obtained with direct-integration techniques, in particular the UHF method. Two-body magnetic interactions represented by the Breit interaction proved to be negligible in effect.