  The phenomenon of shape coexistence is studied in the Relativistic
Hartree-Bogoliubov framework. Standard relativistic mean-field effective
interactions do not reproduce the ground state properties of neutron-deficient
Pt-Hg-Pb isotopes. It is shown that, in order to consistently describe binding
energies, radii and ground state deformations of these nuclei, effective
interactions have to be constructed which take into account the sizes of
spherical shell gaps.
