  The extended Falicov-Kimball model is analyzed exactly in the ground state at
half filling in the limit of large dimensions. In the model the on-site and the
intersite density-density interactions between all particles are included. We
determined the model's phase diagram and found a discontinuous transition
between two different charge-ordered phases. Our analytical calculations show
that the ground state of the system is insulating for any nonzero values of the
interaction couplings. We also show that the dynamical mean-field theory and
the static broken-symmetry Hartree-Fock mean-field approximation give the same
results for the model at zero temperature. In addition, we prove using
analytical expressions that at infinitesimally small, but finite, temperatures
the system can be metallic.
