[DFTB-Plus-User] Kpoint of CNTs

[Bálint Aradi]

Dear Xiaobao,

> Which is right?
> 
> (1)
> KPointsAndWeights = SupercellFolding{
>   1   0   0
>   0   1   0
>   0   0   5
>   0.0 0.0 0.0
>   }
> or
> (2)
>  KPointsAndWeights[relative] = KLines{
>   1 0.0 0.0 0.0
>   4 0.0 0.0 0.5
>   }

The two settings are quite similar, the k-points will only differ
slightly., If your nanotube has a length of 42 A, the sampling above
should be definitely good enough. But you can test it yourself, by
making the sampling finer/coarser and look at the total energy.

> 
> For the CNTs, should I explicitly specify k-points with the correct
> symmetry?

For linear systems that should not be an issue, maybe apart of mirror
symmetry orthogonal to the axis of the tube. However, your cell is large
enough, that it does not matter.

  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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