  We have studied the ionic--neutral curve crossing between the two lowest ^1
Sigma^+ states of LiF in order to demonstrate the efficiency of the quantum
chemistry version of the density matrix renormalization group method (QC-DMRG).
We show that QC-DMRG is capable to calculate the ground and several low-lying
excited state energies within the error margin set up in advance of the
calculation, while with standard quantum chemical methods it is difficult to
obtain a good approximation to Full CI property values at the point of the
avoided crossing. We have calculated the dipole moment as a function of bond
length, which in fact provides a smooth and continuous curve even close to the
avoided crossing, in contrast to other standard numerical treatments.
