Shell evolution at N=20 in the constrained relativistic mean field approach

The shell evolution at N=20,a disappearing neutron magic number observed experimentally in very neutron-rich nuclides,is investigated in the constrained relativistic mean field(RMF) theory.The trend of the shell closure observed experimentally towards the neutron drip-line can be reproduced.The predicted two-neutron separation energies,neutron shell gap energies and deformation parameters of ground states are shown as well.These results are compared with the recent Hartree-Fock-Bogliubov(HFB-14) model and the available experimental data.The perspective towards a better understanding of the shell evolution is discussed.