[CP2K:6432] Problems with GAPW + external potential

Juha Ritala jri... at gmail.com
Thu Apr 30 11:19:19 UTC 2015

Hi Juerg,

thank you for confirming this. Is there any chance that this will be fixed 
in the near future, or should I stick with GPW for the time being? I could 
try and fix it myself, but as far as I understand how GAPW works, 
considering the contribution from the local atomic charges is not at all 

- Juha

On Wednesday, April 29, 2015 at 2:17:45 PM UTC+3, jgh wrote:
> Hi 
> yes, this is a bug. The external potential is applied to the 
> charge on the plane wave grid. In GAPW only the soft part 
> of the charge is on the grid and one would have to also compute 
> the contributions from the local atomic charges. 
> regards 
> Juerg Hutter 
> -------------------------------------------------------------- 
> Juerg Hutter                         Phone : ++41 44 635 4491 
> Institut für Chemie C                FAX   : ++41 44 635 6838 
> Universität Zürich                   E-mail: hut... at chem.uzh.ch 
> Winterthurerstrasse 190 
> CH-8057 Zürich, Switzerland 
> --------------------------------------------------------------- 
> -----cp... at googlegroups.com wrote: -----To: cp... at googlegroups.com 
> From: Juha Ritala 
> Sent by: cp... at googlegroups.com 
> Date: 04/29/2015 09:52AM 
> Subject: [CP2K:6432] Problems with GAPW + external potential 
> I have had some problems when I tried to use GAPW method combined with an 
> external potential. To demonstrate what seems to be the source of the 
> problems, I made this simple test case with a water molecule in a constant 
> external potential. Physically, the constant background potential should 
> not affect the total energy of the water molecule since the molecule is 
> charge neutral. The energy does change as a function of the constant 
> potential when the GAPW method is used, however. You can see this in the 
> attached energy vs. background potential plot. GPW method gives expected 
> behaviour, the total energy stays perfectly constant when the potential is 
> varied. 
> It seems as if some part of the charge in the system is unaffected by the 
> external potential in GAPW and thus the total charge is effectively 
> non-zero. Is this a bug or is there some part of the implementation 
> missing? 
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