Octupole deformation and Ra puzzle with covariant density functional theory in three-dimensional lattice space

Abstract

The anomaly of the residual proton–neutron interaction [Formula: see text] for Ra isotopes around [Formula: see text] deviating from the general trend, the so-called Ra puzzle, is investigated within the framework of covariant density functional theory in three-dimensional lattice space. The potential energy surfaces in [Formula: see text] plane for Ra isotopes are given by the constrained calculations. The average values of proton–neutron interaction [Formula: see text] extracted from the binding energies of Ra and Rn isotopes with axial, triaxial and reflection asymmetric calculations are compared with the data from AME2020 atomic mass evaluation. It is found that the octupole deformation provides a reasonable interpretation of the Ra puzzle.