Triaxially deformed relativistic Hartree-Bogoliubov theory in Woods-Saxon basis

A triaxially deformed relativistic Hartree-Bogoliubov theory in the Woods-Saxon basis is developed with the aim of treating the triaxial deformation, pairing correlations and continuum in a unified way. In order to consider the triaxial deformation, the deformed potentials are expanded in terms of spherical harmonic functions in the coordinate space. In order to take the pairing correlations into account and treat the continuum properly, by using the Dirac Woods-Saxon basis, which has correct asymptotic behavior, the relativistic Hartree-Bogoliubov equation with triaxial deformation is solved. The formalism of triaxially deformed relativistic Hartree-Bogoliubov theory in Woods-Saxon basis is presented. Taking an axially deformed nucleus Ne-24 and a triaxially deformed nucleus Ge-76 as examples, the numerical checks are performed. A weakly bound nucleus Ge-112 is taken as an example to carry out the necessary converge checks for the numerical parameters. In addition, the ground-state properties of even-even germanium isotopes are investigated. The evolutions of two-neutron separation energy, deformation, root-mean-square radii and density distribution with mass number are analyzed. The comparison between the calculations from the relativistic Hartree-Bogoliubov theory based on harmonic-oscillator basis and the triaxially deformed relativistic Hartree-Bogoliubov theory in Woods-Saxon basis is performed. It is found that the neutron drip line is extended from Ge-114 to Ge-118 in the triaxially deformed relativistic Hartree-Bogoliubov theory in Woods-Saxon basis.