BAND MODEL OF ANTIFERROMAGNETISM

We wish to describe antiferromagnetic insulators at T=0 using a one-el ectron approach. To do this, we propose to overcome the inadequacies o f standard local-spin-density theory by adding a spin-dependent magnet ic pseudopotential to the Kohn-Sham equations. We then investigate in a general way using a simple two-dimensional model the physical behavi or to be expected as band occupancy and interaction strength are varie d. We find three phases: nonmagnetic metal, antiferromagnetic metal, a nd antiferromagnetic insulator. We emphasize the transition between la rge and small Fermi surfaces which occurs as the band occupancy change s.