2d coordinate space Hartree-Fock-Bogoliubov calculations for neutron-rich nuclei in the A~100 mass region

Abstract

We solve the Hartree-Fock-Bogoliubov (HFB) equations for deformed, axially symmetric even-even nuclei in coordinate space on a 2D lattice utilizing the Basis-Spline expansion method. Our 2D lattice HFB code is a highly optimized FORTRAN 95 program suitable for parallel supercomputers. We utilize a parallelization scheme for different angular momentum quantum numbers Ω and different isospins. Furthermore, we have reduced the size of the diagonalized Hamiltonian by applying a unitary transformation which decouples the HFB equations. The reduction of the size of the Hamiltonian matrix allows us to calculate even the heaviest systems such as U-238 at a reasonable computation time. Results are presented for the neutron-rich Zirconium and Krypton isotopes up to the two-neutron dripline. In particular, we calculate binding energies, two-neutron separation energies, normal densities and pairing densities, mean square radii, quadrupole moments, and pairing gaps. The results obtained for the Zr isotope chain agree remarkably well with the calculations by Stoitsov et al. In particular both codes agree on the dripline nucleus and predict the same shape change from prolate to spherical. The comparison of rms-radii and neutron densities show also the presence of a neutron skin in the neutron-rich Zr isotope chain. As in the case of Zirconium, we find in the Kr isotope chain a shape change from prolate into oblate deformation, which is reflected in the neutron and proton rms-radius as well. The results obtained for the chain of Kr isotopes confirm that the mass region of A~100 is an area of competition between various coexisting nuclear shapes. In particular we find several different coexisting shapes in three selected Kr nuclei. Such calculations are crucial for astrophysics.