Periodic systems: Fermi level at the band crossing

From: "Konstantin N. Kudin" <kostya[ AT ]rice.edu>
Subject: Periodic systems: Fermi level at the band crossing
Date: Tue, 4 Dec 2001 19:14:53 -0600 (CST)

  Dear colleagues
  This question is almost on the boundary of computational chemistry/solid
 state physics, however, I hope that somebody might be able to help.
  I am looking for examples of metallic 2D and 3D periodic systems that
 have an orbital crossing exactly at the Fermi level. In such a case if the
 exact position of the crossing is missed, the system appears to be an
 insulator (or semiconductor). Any examples, references or even cartesian
 coordinates for unit cells are greatly appreciated.
  Example - 1D periodic (3,3) carbon nanotube
   *     *
    *  *
     *   --- Fermi level
   *  *  --- seeming top of the occupied bands if the crossing is missed
 *     *
  ---->
  k vector
  Thanks a lot!
  Sincerely,
  Konstantin Kudin
  (kostya[ AT ]rice.edu)