Grimme correction and supercell

[Andrzej]

Dear Theo,
thanks for answering my questions.

I have uploaded gra_grim.tar file with inputs and outputs.

The last one (442) is calculated with revpbe, but I think it doesn't
matter, as it uses the same parametrization for Grimmie correction as
pbe.

Andrzej

On Mar 16, 5:13 pm, Teodoro Laino <teodor... at gmail.com> wrote:
> The neighbor list is always built across all possible periodic images
> included within the CUTOFF specified
> for the dispersion (as long as you don't have PERIODIC NONE in the &CELL
> section! this case would
> explain the problem then..)
> .
> The problem must be somewhere else..
> Could you please post a simple input file for both cases (111 and 422) ?
> Thanks
> Teo
>
> Axel wrote:
>
> > On Mar 16, 12:54 pm, Andrzej <kwa... at o2.pl> wrote:
>
> >> Dear users,
>
> >> I performed some calculation for graphite, just for testing some
> >> features.
> >> Here are some results obtained from single point calculations made for
> >> experimenrtal crystal structure under periodic conditions.
> >> Calculations were performed for single unit cell (111), and extended
> >> unit cells: 222, 332 and 442.
>
> >> Here are values of dispersion (Grimme) energy per C atom.
>
> >> 111: -0.004719
> >> 222: -0.0041627
> >> 332: -0.00405803
> >> 442: -0.00405803
>
> >> As the calculations were performed under periodic conditions I would
> >> expected that all these values should be the same. Grimme correction
> >> is purely classical expression independent of electron density,
> >> cutoff,  lack of k-point sampling and so on.
>
> > but it is not independent of minimum image convention and
> > the classical cutoff. i haven't checked the cp2k implementation,
> > but the equivalent code in cpmd would provide an option to
> > compute the real space interactions across multiple copies of
> > the principle unit cell, so that for small unit cells, you
> > would still be able to compute those interactions up to a
> > significant distance beyond the restrictions of using only
> > the closest image.
>
> > cheers,
> >    axel.
>
> >> I will be grateful for any comment.
>
> >> Andrzej