# 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)