The ABINIT Users Mailing List ( CLOSED )

[Anglade Pierre-Matthieu <anglade@gmail.com>]

Dear Thanusit and Jedo,

You are perfectly right : performing band structure calculation in a
primitive cell or in a conventional cell should lead to quite similar
result as long as you perform a converged calculation with respect to
plane wave cut-off and use equivalent k-point sampling. If the
resulting band structures don't look similar, it likely means that you
have not correctly computed the coordinates of your k-points. Try to
take back your paper and pen, write down the coordinates of your
reciprocal space basis vector in both cells (primitive and
conventional) and check for sure that your k-point coordinates
corresponds in both calculation. Once done, you'll find similar result
in both caclulation.

Regards

PMA

2009/11/23 ธนูสิทธิ์ บุรินทร์ประโคน <thanusit@kku.ac.th>:
> Dear all
>
> I have in mind the same question as Jedo's.
>
> I think the initail results of band calculations would look different
> between the primitive cell and the conventional cell. This is because the
> two cells have the Brillouin zones of different sizes and shapes so that the
> k-points sampling used in the band calculation are different. However, since
> we perform the band calculation for the same crystal, both results should
> lead to identical intepretation.  The problem is how?  Is there other points
> I am missing?
>
> All comments or suggestions will be greatly appreciated.
>
>
>
> Regards,
>
> Thanusit Burinprakhon
>
>
>
>
> On November 23, 2009 10:39:13 AM ICT, "Jedo" <jedokim@umich.edu> wrote:
>
> Hi all,
>
> I am trying to compare if I get the same result for primitive cells and
> conventional cell when performing the electronic band structure
> calculation. I may be totally wrong because I am just starting the
> calculation. I am using two different structures, one for conventional
> cell and one for primitive cell. Shouldn't the following structure give
> me the same results? Not sure why I'm getting a totally different band
> structures. Please let me know if I'm just stupid. :) Thanks!!
>
> Primitive cell
>
> #Definition of the unit cell
> -> acell 3*10.217 # This is equivalent to 10.217 10.217 10.217
> -> rprim 0.0 0.5 0.5 # FCC primitive vectors (to be scaled by acell)
> -> 0.5 0.0 0.5
> -> 0.5 0.5 0.0
> ->
> -> #Definition of the atom types
> -> ntypat 1 # There is only one type of atom
> -> znucl 14 # The keyword "znucl" refers to the atomic number of the
> -> # possible type(s) of atom. The pseudopotential(s)
> -> # mentioned in the "files" file must correspond
> -> # to the type(s) of atom. Here, the only type is
> -> Silicon.
> ->
> ->
> -> #Definition of the atoms
> -> natom 2 # There are two atoms
> -> typat 1 1 # They both are of type 1, that is, Silicon.
> -> xred # This keyword indicate that the location of the atoms
> -> # will follow, one triplet of number for each atom
> -> 0.0 0.0 0.0 # Triplet giving the REDUCED coordinate of atom 1.
> -> 1/4 1/4 1/4 # Triplet giving the REDUCED coordinate of atom 2.
>
>
>
>
> Conventional Cell
>
> #Definition of the unit cell
> acell 3*10.217 # This is equivalent to 10.18 10.18 10.18
> rprim 1.0 0.0 0.0 # FCC primitive vectors (to be scaled by acell)
> 0.0 1.0 0.0
> 0.0 0.0 1.0
>
> #Definition of the atom types
> ntypat 1 # There is only one type of atom
> znucl 14 # The keyword "znucl" refers to the atomic number of the
> # possible type(s) of atom. The pseudopotential(s)
> # mentioned in the "files" file must correspond
> # to the type(s) of atom. Here, the only type is Silicon.
>
>
> #Definition of the atoms
> natom 8 # There are two atoms
> typat 1 1 1 1 1 1 1 1 # They both are of type 1, that is, Silicon.
> xred # This keyword indicate that the location of the atoms
> # will follow, one triplet of number for each atom
> 0.0 0.0 0.0
> 1/4 1/4 1/4
> 1/2 1/2 0.0
> 0.0 1/2 1/2
> 1/2 0.0 1/2
> 3/4 3/4 1/4
> 1/4 3/4 3/4
> 3/4 1/2 3/4
>
>
> --
> ================================
> Jedo Kim,
> Heat Transfer Physics Laboratory
> 2350 Hayward, 2186 GG Brown Bldg.
> University of Michigan, Ann Arbor, MI 48109-2143
> Email: jedokim@umich.edu, jdzbox@hotmail.com
> Tel: 734-764-3487 (o); 734-276-8370 (cell)
> ================================
>
>
>
>



-- 
Pierre-Matthieu Anglade