  An interacting boson model Hamiltonian determined from
Hartree-Fock-Bogoliubov calculations with the new microscopic Gogny energy
density functional D1M, is applied to the spectroscopic analysis of
neutron-rich Yb, Hf, W, Os and Pt isotopes with mass $A\sim 180-200$.
Excitation energies and transition rates for the relevant low-lying quadrupole
collective states are calculated by this method. Transitions from prolate to
oblate ground-state shapes are analyzed as a function of neutron number $N$ in
a given isotopic chain by calculating excitation energies, $B$(E2) ratios, and
correlation energies in the ground state. It is shown that such transitions
tend to occur more rapidly for the isotopes with lower proton number $Z$, when
departing from the proton shell closure Z=82. The triaxial degrees of freedom
turn out to play an important role in describing the considered mass region.
Predicted low-lying spectra for the neutron-rich exotic Hf and Yb isotopes are
presented. The approximations used in the model and the possibilities to refine
its predictive power are addressed.
