  We examine a Peierls ground state and its competing metastable state in the
one-dimensional quarter-filled Peierls-Hubbard model with the nearest-neighbor
repulsive interaction V and the electron-phonon interaction (\propto 1/K with K
being the elastic constant). From the mean-field approach, we obtain the phase
diagram for the ground state on the plane of parameters V and K. The coexistent
state of the spin-density wave and the charge ordering is realized for large V
and K. With decreasing K, it exhibits a first-order phase transition to the
unconventional Peierls state which is described by the bond-centered
charge-density-wave state. In the large region of the Peierls ground state in
the phase diagram, there exists the metastable state where the energy takes a
local minimum with respect to the lattice distortion. On the basis of the
present calculation, we discuss the photoinduced phase observed in the
(EDO-TTF)_{2}PF_{6} compound.
