[CP2K-user] [CP2K:21525] Re: Implicit solvent DFT calculation - charge runaway using SCCS

[Marcella Iannuzzi]

Hi Andreas, 

I see that the cell  is very small along z. Where is supposed to be the 
solvent?
Anyway, such small cells are in general problematic without kponts.
Have you tried without SCCS?
Regards
Marcella

On Wednesday, June 4, 2025 at 6:15:47 PM UTC+2 andreas... at gmail.com wrote:

> Hello,thank you for your very fast response. I immediately reran my 
> simulations!
> You are right. My cutoff was quite low, because I played around with the 
> parameters when debugging. Same holds true for OT. I reran my calculations 
> with
> - cutoff 400 Ry
> -No OT to get mixing, with Max_scf=500 still and outer_scf=50, 
> eps_outer=1.0E-5, eps_eigval 1.E-5Are there any other settings which are 
> not too system specific which need to be adjusted, maybe is the convergence 
> criterion too stringent? I am also currently struggling to converge 
> another, larger system (2 layers of the COF structure attached in my first 
> post, 264 atoms in total) where I have done pre-geometric optimization with 
> known forcefields from MD simulations to obtain a decent initial structure.
>
> I attached the updated files and still obtain the problem mentioned above, 
> my charge runs away (I had to restart my simulation, because I did not 
> achieve convergence but the charge runaway happens way before that)
>
> I hope for any discussion on this matter. 
> Thank you very much in advance.
>
> Sincerely, 
> Andreas Doell
>
> Marcella Iannuzzi schrieb am Montag, 2. Juni 2025 um 15:08:20 UTC+2:
>
>> Hello Andreas, 
>>
>> Are you sure that the problem is SCCS? 
>> I ask because the DFT settings seem not to be optimal.
>> In particular, the PW cutoff is very low, which could explain the 
>> incorrect calculation of the electron density and as a consequence of the 
>> total charge.
>>
>> As side comments, the mixing of the density  is not applied when OT is 
>> active.
>>  With OT, it helps running fewer iterations in the inner loop, such that 
>> the preconditioner is updated.
>>
>> Regards
>> Marcella
>>
>>
>>
>> On Monday, June 2, 2025 at 2:00:46 PM UTC+2 andreas... at gmail.com wrote:
>>
>>> My original message was too large, which is why I attach the output in a 
>>> seperate file. Due to its size it seems I have to cut it into pieces, so I 
>>> present the first and last slice of the output where you can observe the 
>>> charge going from 0.000002 to 73, as well as the "Cholesky decomposition 
>>> failed. Matrix ill conditioned ?" after which the run fails.
>>>
>>>
>>> Thanks You all in advance!
>>>
>>> Andreas Döll schrieb am Montag, 2. Juni 2025 um 13:53:44 UTC+2:
>>>
>>>> Hello cp2k community, 
>>>>
>>>> I want to calculate the RESP charges of a structure respecting periodic 
>>>> boundaries in a solvent of epsilon=8. For that I want to do a geometric 
>>>> optimization using the implicit solvent model. However, after some outer 
>>>> SCF iterations I get the following:
>>>>
>>>> *** WARNING in qs_sccs.F:458 :: The system (solute) has a 
>>>> non-negligible ***
>>>>  *** charge of +.000002. It is recommended to use non-periodic boundary 
>>>>   ***
>>>>  *** conditions (PERIODIC none) combined with an appropriate Poisson   
>>>>    ***
>>>>  *** solver (POISSON_SOLVER MT or analytic)
>>>>  
>>>> This charge deviation propagates until the end where I have a charge of 
>>>> 73! 
>>>> I attached input and output file. I do not understand why suddenly I 
>>>> have a leftover charge, which then goes wild. Is it not possible to use 
>>>> SCCS in periodic systems?
>>>>
>>>> Cheers, 
>>>> Andreas
>>>>
>>>>
>>>>

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