Shape evolution in Kr, Zr, and Sr isotopic chains in covariant density functional theory

The relativistic-Hartree-Bogoliubov formalism using density-dependent zero and finite range NN interactions, and separable pairing, is applied to the Kr isotopes (Z = 36) and N = 34-64 isotopes, neutron-rich Sr(Z = 38) and Zr(Z = 40) nuclei with neutron numbers N = 48-70. A systematic search of triaxial ground state and the phenomena of unusual structural change and the coexistence of shape for Kr70-100, and at N = 58 in the Sr86-108 and Zr88-110 isotopes are done. A reasonable agreement is found with the available experimental data and with the macro-microscopic finite range droplet model. The findings are also in good agreement with the self-consistent Hartree-Fock-Bogoliubov calculations based on the interaction Gogny-D1S force, and with relativistic calculations.