[CP2K-user] [CP2K:22099] Re: Energy calculation for charged system LSD/UKS ?

[bmk]

It could be related to your EPS_SCF and EPS_DEFAULT, which are both quite 
high. For DFT-MD I usually set EPS_SCF to 1.0E-6 and EPS_DEFAULT to 
1.0E-12, and for accurate single points I set EPS_SCF to 1.0E-8 and 
EPS_DEFAULT to 1.0E-16. Check 
https://pubs.acs.org/doi/full/10.1021/acs.jpcb.5c05851 section 2.1.4 for 
more details.

The amount of OT inner SCF cycles also seems quite high to me.
Op donderdag 5 februari 2026 om 17:07:27 UTC+1 schreef Andreas Döll:

> Hello, 
> I just want to update people who may have the same question in the future. 
> After further research, my problems could be partially solved with the 
> following changes to my input script: 
>
> ...
> CHARGE +1
>     LSD
>     MULTIPLICITY 1
> ...
> POISSON_SOLVER
> PERIODIC NONE
> ...
> &CENTER_COORDINATES
>         &END
> ...
>
> All of this, and a sufficiently large cutoff (my research shows 5+ A) 
> worked for me for case a) where I have a multiplicity of 1. Centering is 
> there to prevent problems at the edge of the box with the solver.
> Sadly for system b) where the multiplicity is higher, I always get the 
> usual wavelet solver issue, even though I 
>
> a) Center my atoms
> b) Have a large box (more than 10 A from edges even)
> c) have a large cutoff
>
> I keep getting problems with the Wavelet solver at the edge: Usually, the 
> error message
>
>  *** WARNING in ps_wavelet_methods.F:238 :: Density non-zero on the edges 
> ***
>  *** of the unit cell: wrong results in WAVELET solver                   
>  ***
>
> can be treated with a larger box, it seems to me from looking around the 
> Cp2kgroup that higher multiplicity might be difficult, but even when 
> increasing the box to have *20+ A vacuum* in each direction I still get a 
> problem at the edge. I attach my input script for this issue, maybe 
> somebody can spot some obvious mistake quickly! Is this maybe a chemistry 
> issue (getting multiplicity wrong? I just cut out a molecule off a larger 
> structure, so at each branch of the Triazine, a Hydrogen is missing)
>
> Thank you for your patience
> Andreas Döll schrieb am Mittwoch, 4. Februar 2026 um 11:46:43 UTC+1:
>
>> Dear cp2k community,
>>
>> I have two charged systems I want to perform a single energy calculation.
>>
>> System a) Neutral molecule with a Lithium at some distance
>> System b) Charged molecule (cut out of a larger molecular structure, so 3 
>> Hydrogens are missing) 
>>
>> For both calculations, my energy either diverges or makes jumps. 
>> Usually I have performed calculations with neutral molecules, not charged 
>> systems, so I am not familiar with the proper procedure. I followed the 
>> example give here https://www.cp2k.org/exercises:2014_ethz_mmm:hfx_h2ion 
>> I defined my Charge in the DFT section, as well as using LSD option and 
>> switched to a Nonperiodic system - as far as I understand this is 
>> necessary? Do I need to define the multiplicity of my system as well ?
>>
>> Cheers, 
>> Andreas
>>
>>
>>

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