[DFTB-Plus-User] question on Ewald summation in coulomb.F90

[Wei Lai]

Dear Balint,

Thanks for your reply.  If the calculation is correct, I think those
factors of 2 are for the matrix form where there is double counting.  They
were removed later when the total coulmobic energy was calculated.

Thanks, Wei

On Mon, Jan 7, 2019 at 6:12 AM Bálint Aradi <aradi at uni-bremen.de> wrote:

> Dear Wei,
>
> the calculation of the Ewald is for sure correct, as you obtain the
> correct Madelung energy with it. (I just checked it for simple cubic
> lattice).
>
> You should take into account, that ususally we only sum over the half of
> the Brillouin-zone, which must be compensated by a factor of two in the
> reciprocal part. I am not sure, where the other factor 2's are comming
> from, it could be the energy units? (Hartree vs. Rydberg?)
>
>   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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