[CP2K-user] [CP2K:21382] Re: Struggling to converge single atom calculation

[Harry Richardson]

Hi Frederick, 

Thank you so much for your support. I read the wb97X-D paper and came up 
with the following settings for HF.    

    &HF
    FRACTION 0.22                ! From wB97X-D paper
    &SCREENING
      EPS_SCHWARZ 1.0E-10      ! affects convergence / accuracy? (choose 
same as WB97X_2LP.sec)
    &END SCREENING
    &INTERACTION_POTENTIAL
      POTENTIAL_TYPE TRUNCATED
      CUTOFF_RADIUS 10.0           ! (didn't see mentioned in paper choose 
same as WB97X_2LP.sec)
      OMEGA 0.2                ! From wB97X-D paper
    &END INTERACTION_POTENTIAL
  &END HF

With these settings the calculation has converged, the only thing i am not 
sure about is if I need to scale the coulomb and longrange as is done 
within WB97X_2TQZ.sec, do I need to use a mixed interaction potential? 

          SCALE_COULOMB 0.678792
          SCALE_LONGRANGE 0.321208

the paper mentions:
"one first defines long-range LR  and short-range  SR  operators to 
partition the Coulomb operator"

 but i couldn't see exact values listed anywhere?

Thanks again for all your help, I owe you a beer!

On Thursday, April 17, 2025 at 12:42:02 PM UTC+1 Frederick Stein wrote:

> Dear Harry,
> Consider them an inspiration as wB97X-2 is a double-hybrid functional, 
> i.e. it has an additional MP2 correlation contribution and requires a 
> rather different amount of HF exchange. Read the paper defining wB97X (and 
> potentially also wB97X-2) how to set up the parameters.
> HTH,
> Frederick
>
> Harry Richardson schrieb am Donnerstag, 17. April 2025 um 13:24:50 UTC+2:
>
>> Thank you very much for your response Frederick, 
>>
>> I see there are some xc_sections that use the omega97X-D functional, 
>> Do you think either:
>> WB97X_2LP.sec 
>> <https://github.com/cp2k/cp2k/blob/master/data/xc_section/WB97X_2LP.sec> 
>> or WB97X_2TQZ.sec 
>> <https://github.com/cp2k/cp2k/blob/master/data/xc_section/WB97X_2TQZ.sec>
>> may be suitable, or would it be better to define it myself. 
>>
>>
>> Thanks again 
>> Harry 
>> On Thursday, April 17, 2025 at 12:04:05 PM UTC+1 Frederick Stein wrote:
>>
>>> Dear Harry,
>>> You have to setup a suitable HF section (see 
>>> https://manual.cp2k.org/trunk/CP2K_INPUT/FORCE_EVAL/DFT/XC/HF.html). 
>>> CP2K will not do it by itself except of an available shortcut as stated in 
>>> the manual (see 
>>> https://manual.cp2k.org/trunk/CP2K_INPUT/FORCE_EVAL/DFT/XC/XC_FUNCTIONAL.html). 
>>> Compare the already available xc_sections in the CP2K data directory (
>>> https://github.com/cp2k/cp2k/tree/master/data/xc_section) for their 
>>> setup.
>>> Best,
>>> Frederick
>>>
>>> Harry Richardson schrieb am Donnerstag, 17. April 2025 um 11:15:16 UTC+2:
>>>
>>>> i have been suggested to use multiplicity 3, I have tried and does not 
>>>> affect convergence, please see attached. 
>>>>
>>>> On Thursday, April 17, 2025 at 9:36:10 AM UTC+1 Harry Richardson wrote:
>>>>
>>>>> Hi all, I am pretty new to DFT and trying to run some single atom (C) 
>>>>> DFT to use as a subtraction when fine tuning a machine learned force field 
>>>>> for MD. As such it needs to be run at the same level of theory as my full 
>>>>> system calculations. 
>>>>>
>>>>> I just need single point energies. 
>>>>>
>>>>> At the moment it is not converging, I have attached my input and 
>>>>> output files, i am using the omega97X-D functional. 
>>>>>
>>>>> Some thing I have tried include: 
>>>>>
>>>>>    - Changing the box from periodic to non periodic
>>>>>    - Reducing mixing
>>>>>    - Increasing & decreasing the size of the box 
>>>>>    - Changing multiplicity 
>>>>>    - Reducing cutoff 
>>>>>    
>>>>> The energy change per step seems to reduce over steps but does not 
>>>>> converge. 
>>>>>
>>>>> I am using the DZVP-MOLOPT basis set and GTH-PBE-q4 potential as 
>>>>> suggested in here: https://www.cp2k.org/exercises:2018_uzh_cmest:faq 
>>>>> potentially that is the issue? 
>>>>>
>>>>> Would appreciate any help you can provide 
>>>>>
>>>>> Thanks
>>>>>
>>>>

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