  The location of the neutron drip line, currently known for only the lightest
elements, remains a fundamental question in nuclear physics. Its description is
a challenge for microscopic nuclear energy density functionals, as it must take
into account in a realistic way not only the nuclear potential, but also
pairing correlations, deformation effects and coupling to the continuum. The
recently developed deformed relativistic Hartree-Bogoliubov theory in continuum
(DRHBc) aims to provide a unified description of even-even nuclei throughout
the nuclear chart. Here, the DRHBc with the successful density functional
PC-PK1 is used to investigate whether and how deformation influences the
prediction for the neutron drip-line location for even-even nuclei with
8<=Z<=20, where many isotopes are predicted deformed. The results are compared
with those based on the spherical relativistic continuum Hartree-Bogoliubov
(RCHB) theory and discussed in terms of shape evolution and the variational
principle. It is found that the Ne and Ar drip-line nuclei are different after
the deformation effect is included. The direction of the change is not
necessarily towards an extended drip line, but rather depends on the evolution
of the degree of deformation towards the drip line. Deformation effects as well
as pairing and continuum effects treated in a consistent way can affect
critically the theoretical description of the neutron drip-line location.
