  Following the discovery of the Fe-pnictide superconductors, LDA band
structure calculations showed that the dominant contributions to the spectral
weight near the Fermi energy came from the Fe 3d orbitals. The Fermi surface is
characterized by two hole surfaces around the $\Gamma$ point and two electron
surfaces around the M point of the 2 Fe/cell Brillouin zone. Here, we describe
a 2-band model that reproduces the topology of the LDA Fermi surface and
exhibits both ferromagnetic and $q=(\pi,0)$ spin density wave (SDW)
fluctuations. We argue that this minimal model contains the essential low
energy physics of these materials.
