[CP2K-user] [CP2K:16620] Re: EXTERNAL_POTENTIAL

[Бранислав Миловановић]

Thanks a lot for clarifying!

If would be useful if someone added these into the reference manual 
description.

On Monday, February 21, 2022 at 5:09:16 PM UTC+1 mattwa... at gmail.com wrote:

> 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 certainly.
> Matt
>
> 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:
>>
>>   &EXTERNAL_POTENTIAL
>>     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
>>     PARAMETERS A B Z0
>>   &END EXTERNAL_POTENTIAL
>>
>> 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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