  We analyze the itinerant model for antiferromagnetism, which was developed
previously by Plischke, Mattis, Brouers and Mizia. In this model we include
both; single-site and two-site electron correlations. Including additionally
band degeneration into the model allows for considering intra-atomic exchange
interactions in the Hamiltonian. The modified Hartree-Fock approximation for
the two-site interactions is used. This approximation gives the spin band
narrowing, which is the same for both spin directions and affects possibility
of antiferromagnetic ordering. We use the Green function technique and CPA
decoupling. This allows for the change in shape of the spin bands, described by
the correlation factors, which decreases kinetic energy of the system. The
effective Hartree field and the gain in kinetic energy due to the on-site and
inter-site correlation factors drive the antiferromagnetism.
