  Nuclear masses of even-even nuclei with the proton number $8\leq Z\leq 50$ (O
to Sn isotopes) from proton drip line to neutron drip line are investigated
using the triaxial relativistic Hartree-Bogoliubov (RHB) theory with the
relativistic density functional PC-PK1, and the dynamical correlation energies
(DCEs) associated with the rotational motion and the quadrupole shape
vibrational motion are taken into account by the five-dimensional collective
Hamiltonian (5DCH) method. The root-mean-square deviation with respect to the
experimental masses reduces from 2.50 MeV to 1.59 MeV after the consideration
of DCEs. The inclusion of DCEs has little influence on the position of drip
lines, and the predicted numbers of bound even-even nuclei between proton and
neutron drip lines from O to Sn isotopes are respectively 569 and 564 for the
cases with and without DCEs.
