  Simple hexagonal graphite, also known as AA graphite, is a metastable
configuration of graphite. Using tight-binding approximation it is easy to
demonstrate that AA graphite is a metal with well-defined Fermi surface. The
Fermi surface consists of two sheets, each shaped like a rugby ball. One sheet
corresponds to electron states, another corresponds to hole states. The Fermi
surface demonstrates good nesting: a suitable translation in the reciprocal
space superposes one sheet onto another. In the presence of the
electron-electron repulsion a nested Fermi surface is unstable with respect to
spin-density wave ordering. This instability is studied using the mean-field
theory at zero temperature, and the spin-density wave order parameter is
evaluated.
