SD-SHELL STUDY WITH A MULTICONFIGURATION MIXING APPROACH DESIGNED FORLARGE-SCALE NUCLEAR-STRUCTURE CALCULATIONS

A systematic numerical investigation of a recently developed nuclear s tructure approach is presented which diagonalizes the Hamiltonian in t he space of the symmetry-projected Hartree-Fock-Bogoliubov (HFB) vacuu m and symmetry-projected quasiparticle excitations with respect to it. The underlying HFB transformation, which is assumed to-be time-revers al and axially symmetric, is determined by variation after the project ion. The model allows the use of large basis systems. It has been appl ied to the calculation of energy spectra of several even-even, odd-odd , and odd mass nuclei in the sd shell with mass numbers reaching from A=20-30. The Chung-Wildenthal interaction has been used. Good agreemen t with the exact shell model diagonalization and a considerable improv ement on a previous approach, where the HFB transformation was signifi cantly more restricted, is obtained.