  We consider a modified extended Hubbard model (EHM) which, in addition to the
on-site repulsion U and nearest-neighbor repulsion V, includes polarization
effects in second-order perturbation theory. The model is equivalent to an EHM
with renormalized U plus a next-nearest-neighbor repulsion term. Using a method
based on topological quantum numbers (charge and spin Berry phases), we
generalize to finite hopping t the quantum phase diagram in one dimension
constructed by van den Brink et al. (Phys. Rev. Lett. 75, 4658 (1995)). At
hopping t=0 there are two charge density-wave phases, one spin density-wave
phase and one intermediate phase with charge and spin ordering, depending on
the parameter values. At t \neq 0 the nature of each phase is confirmed by
studying correlation functions. However, in addition to the strong-coupling
phases, a small region with bond ordering appears. The region occupied by the
intermediate phase first increases and then decreases with increasing t, until
it finally disappears for t of the order but larger than U. For small t, the
topological transitions agree with the results of second order perturbation
theory.
