The generalized hybrid derivative coupling model is applied to study the ground-state deformation and binding energy of even-even Ne, Mg, Si, and S isotopes. The energy surface is plotted as a function of the axial deformation.The deformation values predicted in the present calculation are closer to experimentally observed values in most nuclei in this region in comparison to other relativistic calculations. The ground state binding energy prediction, in contrast, is poorer. A number of nuclei, like ${}^{18,28}\mathrm{Ne},$ ${}^{20}\mathrm{Mg},$ ${}^{36}\mathrm{Si},$ and ${}^{38,54}\mathrm{S},$ may be triaxial in their ground state. The shape of the nuclei with $N=20\mathrm{}$ cannot be explained at the mean-field level and neutron excitation across the shell gap is expected to play a major role. The neutron number $N=8\mathrm{}$ may no longer be a magic number in the drip line nuclei in this region.

• Received 23 November 2001

DOI:https://doi.org/10.1103/PhysRevC.65.034329