  We explore the evolution of the structure of the ground state of a nucleus
with two valence nucleons as the system approaches the two particle threshold.
We use a three-body model of $core+n+n$ where the core is deformed and allowed
to excite. We find that both NN correlations and correlations due to
deformation/excitation of the core inhibit the formation of halos. Our results
suggest that it is unlikely to find halo nuclei on the dripline of deformed
nuclei.
