  Real-time dynamics of charge density and lattice displacements is studied
during photoinduced ionic-to-neutral phase transitions by using a
one-dimensional extended Peierls-Hubbard model with alternating potentials for
the one-dimensional mixed-stack charge-transfer complex, TTF-CA. The
time-dependent Schr\"odinger equation and the classical equation of motion are
solved for the electronic and lattice parts, respectively. We show how neutral
domains grow in the ionic background. As the photoexcitation becomes intense,
more neutral domains are created. Above threshold intensity, the neutral phase
is finally achieved. After the photoexcitation, ionic domains with wrong
polarization also appear. They quickly reduce the averaged staggered lattice
displacement, compared with the averaged ionicity. As the degree of initial
lattice disorder increases, more solitons appear between these ionic domains
with different polarizations, which obstruct the growth of neutral domains and
slow down the transition.
