Unrestricted symmetry-projected Hartree-Fock-Bogolyubov calculations for SD-shell nuclei

The solution of the Hartree-Fock-Bogoliubov problem with restoration of the broken symmetries before the variation has been generalized for the use of totally unrestricted quasi-particle determinants. With this method doubly-even, doubly-odd and odd nuclei can be treated on the same footing. Comparison with the results of complete shell-model diagonalizations shows that already one-determinant representations yield a very good approximation to the exact solutions even in the middle of the 1s0d shell. The problem is especially suited for numerical implementation on parallel computers. First tests show a linear dependence of the inverse CPU time with the number of processors used. (orig.)