[DFTB-Plus-User] Calculation of Kpoints

[Ben Hourahine]

Hello Mat,

yes that also works.

Regards

Ben

On 13/11/2020 14:42, Mat Toliday via DFTB-Plus-User wrote:
> Dear Bálint,
> Am I correct in thinking that the calculation can be split up further
> by the number of spin channels?
> Mat Tolladay
> On Friday, 13 November 2020, 10:48:30 CET, Bálint Aradi
> <aradi at uni-bremen.de> wrote:
>
>
> Dear Carlo,
>
> > As far as I understood the best value of *n* should be a multiple of
> > Kpoints, if possible.
>
> That's true, but only if you use process groups (Parallel/Groups). If
> you for example have nK K-points and nProc processes (with nProc = n *
> nK), then creating n groups would be the most efficient parallelisation.
>
>
> > My question is: *is there any way to compute in advance the number of
> > Kpoints without running dftb+?*
>
>
> Since DFTB+ only reduces the K-points by the inversion symmetry, it is
> often easy to guess nr. of k-points in advance. For the commonly used
> MP-scheme with
>
> SupercellFolding {
>   n1 0 0
>   0 n2 0
>   0  0 n3
>   s1 s2 s3
> }
>
> it would be
>
> - (n1 * n2 * n3) / 2 if n1, n2, n3 are even and s1 = s2 = s3 = 0.5
>
> - (n1 * n2 * n3 + 1) / 2 if n1, n2, n3 are odd and s1 = s2 = s3 = 0.0
>   or s1 = s2 = s3 = 0.5
>
> - and probably (n1 * n2 * n3) in most other cases.
>
>
> Best regards,
>
> Bálint
>
>
> Ps. In case, you are interested to contribute: It would actually not too
> complicated to assamble a small tool, which parses the DFTB+ input and
> spits out the k-points.
>
> -- 
> 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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>
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-- 
        Dr.  B.  Hourahine,  Senior  lecturer
            SUPA, Department  of  Physics,
             University  of  Strathclyde,
              John  Anderson  Building,
          107 Rottenrow, Glasgow G4 0NG, UK.                    
  +44 141 548 2325, benjamin.hourahine at strath.ac.uk

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