[CP2K-user] [CP2K:16669] Re: Point charges to simulate an electric field?

[Бранислав Миловановић]

Thanks.
OK, I think I get it now. 
So I have set CHARGE keyword to 25, since I want to have 25 fake H atoms 
and each to represent smeared charge of +0.28e, and the rest of my system 
in neutral.
My KIND section now:






*    &KIND X      ELEMENT H      BASIS_SET NONE      POTENTIAL GTH-PBE-q1  
    CORE_CORRECTION -0.88    &END KIND*

However, when I perform population analysis I find finite population on 
these fake atoms:

                           









*Hirshfeld Charges  #Atom  Element  Kind  Ref Charge     Population         
           Net charge      1       H      1       0.280          0.046     
                    0.234      2       H      1       0.280          0.047 
                        0.233      3       H      1       0.280         
 0.052                         0.228      4       H      1       0.280     
     0.055                         0.225      5       H      1       0.280 
         0.046                         0.234      6       H      1       
0.280          0.051                         0.229.*
*.*
*.*

How is this possible when they are described with no basis at all?

Best,
BM

On Wednesday, March 2, 2022 at 5:04:08 PM UTC+1 mattwa... at gmail.com wrote:

> There will be the core charge of the original atom as well - so you need 
> neutralise the atom core (-1 in your case) then add your charge back.
> Yes - the charge keyword will alter the number of electrons in the system 
> so if you want these to be virtual protons not hydrogen atoms then you do 
> need to remove the electron as well with the charge keyword.
> If your overall system is charged then normal issues of charged periodic 
> systems apply.. 
> Matt
>
> On Monday, 28 February 2022 at 12:37:58 UTC dr.bra... at gmail.com wrote:
>
>> Additionally, should I in such cases change total charge od the system?
>>
>> On Wednesday, February 23, 2022 at 2:09:59 PM UTC+1 Бранислав Миловановић 
>> wrote:
>>
>>> Thanks, just want to check if this is right way to do this:
>>> I defined atoms labeled *X* in the coord file and then I added this 
>>> section into the SUBSYS:
>>>
>>>     &KIND X
>>>       ELEMENT H
>>>       GHOST .TRUE.
>>>       BASIS_SET NONE
>>>       POTENTIAL GTH-PBE-q1
>>>       CORE_CORRECTION 0.12   # 3/25
>>>     &END KIND
>>>
>>> Is this the right way to divide for example 3*e* charge over 25 fake 
>>> hydrogen atoms?
>>>
>>> Branislav
>>>
>>> On Monday, February 21, 2022 at 4:31:49 PM UTC+1 mattwa... at gmail.com 
>>> wrote:
>>>
>>>> Multiple options - most directly:
>>>>
>>>> https://manual.cp2k.org/cp2k-9_1-branch/CP2K_INPUT/FORCE_EVAL/SUBSYS/KIND.html#list_CORE_CORRECTION
>>>> lets you change the core charge on a pseudopotential. If you make a 
>>>> fake hydrogen and adjust charge appropriately you'd get close to what you 
>>>> were after (won't be a point charge but gaussian smeared charge).
>>>>
>>>> There are other routines that could load an external potential on a 
>>>> grid or make use of the QM/MM code in some form.
>>>> Matt
>>>>
>>>>
>>>> On Monday, 21 February 2022 at 15:24:34 UTC dr.bra... at gmail.com wrote:
>>>>
>>>>> Dear cp2k users,
>>>>>
>>>>> Is it possible to introduce ghost atoms with no basis set and with 
>>>>> finite non-integer point charge in AIMD calculations? Something like MM 
>>>>> point charges.
>>>>>
>>>>> I want to try to simulate behaviour of some small molecules in the 
>>>>> electric field which originates from a particular sequence of the point 
>>>>> charges.
>>>>>
>>>>> Thanks
>>>>> Branislav
>>>>>
>>>>

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