[CP2K:2785] Multigrid

Juerg Hutter hut... at pci.uzh.ch
Thu Jul 29 16:46:03 CEST 2010


Hi

the accuracy is controlled by the cutoff and (if there are
multigrids) the relative cutoff (REL_CUTOFF). The relative cutoff
is used to decide what grid is used for a product of basis functions.
If the relative cutoff is converged the actual number of grids
does not matter (for accuracy). If your relative cutoff is too low
you will see large differences when changing the number of
grids.

best regards

Juerg Hutter


----------------------------------------------------------
Juerg Hutter                   Phone : ++41 44 635 4491
Physical Chemistry Institute   FAX   : ++41 44 635 6838
University of Zurich           E-mail: hut... at pci.uzh.ch
Winterthurerstrasse 190
CH-8057 Zurich, Switzerland
----------------------------------------------------------


On Thu, 29 Jul 2010, cbeck wrote:

> Hello all,
>
> I'm still trying to wrap my head around the use of the multigrids
> CP2K.   From my understanding if I were to go from using 4 grids to 2,
> it would affect the efficiency of the calculation.  However, I don't
> know if that would affect the accuracy of the results (given the fact
> that the finest grid remains the same between the two calculations).
> Can someone tell me if changing the number of multigrids affects the
> accuracy of a calculation?
>
> Thanks,
> Corey
>
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