  We investigate the possibility of describing triaxial quadrupole deformations
for nuclei close to the two-neutron drip line by the Hartree-Fock Bogoliubov
method taking into account resonances in the continuum. We use a Skyrme
interaction to describe the Hartee-Fock hamiltonian and a density-dependent
zero-range interaction to evaluate the pairing field. The mean-field equations
are solved in a three-dimensional cubic mesh. We study the stability of the
two-neutron separation energies and of the description of the nuclear surface
as a function of the number of active mean-field orbitals and of the size of
the mesh. The even Ni isotopes are used as a test case and the accuracy as a
function of quadrupole deformation is studied by performing constrained
calculations. A first application to the study of the two-neutron separation
energies in Ni isotopes up to the drip line is presented.
