[DFTB-Plus-User] Electric field in periodic calculations

[Bálint Aradi]

Dear Sébastien,

> I am currently trying to use the external electric field for periodic
> calculations.
> My system is a slab normal to z direction, with a big vacuum to avoid
> interactions.
> I would like to apply an external electric field along z direction, and
> I have some questions:
> 
> 1- Do I have to set the vacuum layer to be quite infinite to be sure the
> field to be constant 20 A° around the supercell's center?
> 2- My supercell is monoclinic. Each time I try to launch a calculation I
> have the following message: "Interaction between atoms .. and .. crosses
> the saw-tooth discontinuity in the electric field." whatever the
> position of the supercell origin... What do I do wrong? Or is it just an
> uncompatibility with monoclinic cells?

 The external field is overall homogeneous (constant), apart of the
discontinuity in the z=0 plane. The potential is accordingly a saw-tooth
potential, with a jump in the same plane. So, every atom of your slab
should have a positive z coordinates.

 As of the vacuum: the vacuum should be big enough, that no interaction
between atoms in different unit cells occur along this direction.

  Best regards,

  Bálint



-- 
Dr. Bálint Aradi
Bremen Center for Computational Materials Science, University of Bremen
http://www.bccms.uni-bremen.de/cms/people/b_aradi/


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