[CP2K:6441] Problems with GAPW + external potential

[Matt W]

Hi Juha,

there are a couple of files attached (compatible with latest version of 
cp2k at time of writing, but there are only a couple of lines changed) you 
can try and see if it works with GAPW. It only works with the soft part of 
the density, including the compensation charges. As the compensation 
charges, including the core, are put onto the fft grid the core routines in 
external_potential need to be protected. Might need tidying for mixed 
gpw/gapw.

I guess this approximately means that the core (i.e. any functions on the 
hard atomic grids) isn't directly polarized by the field? For modest fields 
it should be fine, maybe?

Let me know how it goes,

Matt


On Friday, May 1, 2015 at 3:46:30 PM UTC+1, jgh wrote:
>
> Hi 
>
> unfortunately, I don't have time to look into this. 
> It seems to me that for analytic potentials it wouldn't be that hard, 
> but for potentials read in on a grid it would need special care. 
>
> regards 
>
> Juerg 
> -------------------------------------------------------------- 
> 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 
> <javascript:> 
> Winterthurerstrasse 190 
> CH-8057 Zürich, Switzerland 
> --------------------------------------------------------------- 
>
> -----cp... at googlegroups.com <javascript:> wrote: -----To: 
> cp... at googlegroups.com <javascript:> 
> From: Juha Ritala 
> Sent by: cp... at googlegroups.com <javascript:> 
> Date: 04/30/2015 01:18PM 
> Subject: Re: [CP2K:6441] Problems with GAPW + external potential 
>
> 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 
> trivial. 
>
> - 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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>
> [attachment "E_vs_V_GAPW_and_GPW.pdf" removed by Jürg Hutter/at/UZH] 
>
> [attachment "H2O_constant_extpot_GPW.inp" removed by Jürg Hutter/at/UZH] 
>
> [attachment "H2O_constant_extpot_GPW.out" removed by Jürg Hutter/at/UZH] 
>
> [attachment "H2O_constant_extpot_GAPW.inp" removed by Jürg Hutter/at/UZH] 
>
> [attachment "H2O_constant_extpot_GAPW.out" removed by Jürg Hutter/at/UZH] 
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