  The two-basis method to solve the HFB for deformed nuclei in coordinate space
is examined concerning the precision of the density tail. Small cutoff energies
are shown to give rise to ripples in the tail, whose wave length corresponds to
the cutoff momentum. More precise solutions require higher cutoff energies,
which result in HFB matrices of larger dimensions. To circumvent the difficulty
of the large dimension, we employ another method to solve the HFB ---the
natural-orbital method introduced originally for spherical nuclei--- to apply
it to deformed nuclei. The method can be successfully implemented with a
three-dimensional Cartesian mesh representation.
