Shell-model and Hartree-Fock calculations for even-mass O, Ne, and Mg nuclei

Shell-model and deformed Hartree-Fock plus BCS calculations are reported for even-even nuclei O18-30, Ne18-36, and Mg20-42; shell-model calculations additionally included Ne-38,Ne-40 and Mg-44,Mg-46,Mg-48. Ground-state binding energies and 2(1)(+) quadrupole moments are calculated by bath models. Shell-model calculations, aided by a new truncation method, include 2(1)(+) excitation energies and magnetic moments. Hartree-Fock calculations with SkI6, RATP, Z*(sigma), and SkI6 Skyrme forces include ground-state deformations and rms radii; SkI6 gives the best overall agreement with experiment. The two models are compared with each ether and with experiment. Two-neutron separation energies, evidence for a neutron halo or skin in heavy O isotopes, and deformation of Ne and Mg isotopes are discussed. Both models indicate disappearance of the shell gap at N = 28 (Mg), and the shell model does so additionally at N = 20 (Ne and Mg). [S0556-2813(99)05109-2].