  We study the two-neutron correlations in the ground state of the weakly-bound
two-neutron halo nucleus $^{22}$C sitting at the edge of the neutron-drip line
and also in the unbound nucleus $^{26}$O sitting beyond the neutron dripline.
For the present study, we employ a three-body (core$+n+n$) structure model
designed for describing the two-neutron halo system by explicit inclusion of
unbound continuum states of the subsystem (core$+n$). We use either a
density-independent or a density-dependent contact-delta interaction to
describe the neutron-neutron interaction and its strength is varied to fix the
binding energy. We report the configuration mixing in the ground state of these
systems for different choices of pairing interactions.
