Matt Watkins mattwatkinsuk at gmail.com
Mon Feb 21 16:09:16 UTC 2022

I'd need to check the exact details as I've forgotten:
The one inside the DFT section will operate on both electrons and atomic 
cores in a DFT calculation - so it pretty much corresponds to adding an 
electric field.
The one inside the FORCE_ENV I _think_ will only operate on cores and is 
mainly designed for use in the MM code or non-grid based methods. 
If you are doing a DFT calc you want the one inside the DFT section, almost 

On Monday, 14 February 2022 at 15:32:44 UTC dr.bra... at gmail.com wrote:

> Dear cp2k community,
> I'm confused about two EXTERNAL_POTENTIAL sections:
> https://manual.cp2k.org/cp2k-9_1-branch/CP2K_INPUT/FORCE_EVAL/EXTERNAL_POTENTIAL.html
> and
> https://manual.cp2k.org/cp2k-9_1-branch/CP2K_INPUT/FORCE_EVAL/DFT/EXTERNAL_POTENTIAL.html
> I notice differences between keywords and subsections and I want to 
> simulate interaction of different solutes in the bulk water with the 
> polarized graphene suface.
> My section within the FORCE_EVAL:
>     ATOMS_LIST 61..363                      # applied only on waters 
> present in the system
>     FUNCTION (A/B)*exp(-Z/Z0)         # potential that decays exponentially
>     VALUES [eV] -3.0 [angstrom] 1.0 [angstrom] 6.0
> With this setup I noticed that the total energy is lower compared when no 
> external potential is present and water molecules interact in the way I 
> expected.
> So, the questions are:
> 1) Is this the right way to simulate interaction with the electric field 
> that originate from some surface, or should I employ EFIELD keywords or 
> something similar?
> 2) Do I need to define EXTERNAL_POTENTIAL section within the DFT section 
> as well, since I don't need some of the specific options there?
> 3) Could someone explain how PBC are entangled with the EXTERNAL_POTENTIAL?
> Thanks,
> Branislav

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