Quantum Monte Carlo methods are used to study a quantum phase transition in
a one-dimensional Hubbard model with on-site interaction U and a staggered
ionic potential (Delta). Using recently formulated methods, the electronic
polarization and localization are determined directly from the correlated
ground state wave function and compared to results of previous work using e
xact diagonalization and Hartree-Fock. We find a transition from a symmetri
c band insulator to a broken-symmetry bond ordered (BO) phase as the ratio
of U/Delta is increased, with a metallic point at the transition. Since it
is known that at Delta = 0 the usual Hubbard model is a Mott insulator (MI)
with no long-range order, we have searched for a second transition to this
state by (i) increasing U at fixed Delta and (ii) decreasing Delta at fixe
d U. We find no transition from the BO to MI state, and we propose that the
symmetric MI state exists only at Delta = 0.