BAND MODEL OF ANTIFERROMAGNETISM

We wish to describe antiferromagnetic insulators at T=0 using a one-electron approach. To do this, we propose to overcome the inadequacies of standard local-spin-density theory by adding a spin-dependent magnetic pseudopotential to the Kohn-Sham equations. We then investigate in a general way using a simple two-dimensional model the physical behavior to be expected as band occupancy and interaction strength are varied. We find three phases: nonmagnetic metal, antiferromagnetic metal, and antiferromagnetic insulator. We emphasize the transition between large and small Fermi surfaces which occurs as the band occupancy changes.