  The rich novel materials class of iron based superconductors turned out to
exhibit a very complex electronic structure, despite of the simplicity of their
crystal structures. For various approaches to study the instability against
magnetic order or superconductivity, a real space description of the electronic
structure is required. Here, the bonding situation and the orbital structure of
the electronic state are analyzed and minimum tight-binding models
quantitatively correctly describing the low-energy electronic structure are
provided.

Superconductivity