  Exact ground-state properties are presented by combining the diagonalization
in the Fock space (and taking all hopping integrals and all two-site
interactions) with the ab initio optimization of the Wannier functions.
Electrons are essentially localized for the interatomic distance R~2A for
s-like states, when the quasiparticle mass is divergent. The momentum
distribution dispersion is proposed to define the localization order parameter.
Dimerization and zero-point energies are also discussed. The method provides
convergent results for N>=8 atoms.

Strongly Correlated Electrons