[CP2K-user] [CP2K:15365] Problem converging SCF for a system containing Fe2+

[Pierre-André Cazade]

Hi Salome,

I agree with Matt. Try OT:


and if you still prefer to use the default solver, use Broyden Mixing
instead of P-mixing.

    &SCF
      SCF_GUESS  ATOMIC
      &MIXING
        METHOD BROYDEN_MIXING
        ALPHA 0.4
        BETA 0.5
        NBROYDEN 8
        NMIXING 2
      &END MIXING
    &END SCF

It should be CHARGE 2 and MULTIPLICITY 0.

     &SCF
       MAX_SCF  20
       SCF_GUESS  ATOMIC
       &OT  T
         MINIMIZER  CG
         PRECONDITIONER  FULL_ALL
       &END OT
       &OUTER_SCF  T
         MAX_SCF  100
       &END OUTER_SCF
     &END SCF

Try increasing the CUTOFF to 500 or 600.

Regards,
Pierre

On Fri, May 14, 2021 at 1:29 PM Matt W <mattwa... at gmail.com> wrote:

> Reduce the ALPHA value in &SCF / &MIXING
>
>
> https://manual.cp2k.org/cp2k-8_1-branch/CP2K_INPUT/FORCE_EVAL/DFT/SCF/MIXING.html
>
> the default is much to large and causes the oscillations.
>
> OT is often a faster / more reliable solver for non-metals.
>
> Matt
>
> On Friday, May 14, 2021 at 12:37:44 PM UTC+1 salo... at gmail.com wrote:
>
>> Hi Pierre,
>>
>> Thank you so much for your answer,
>>
>> I have added all your suggestions:
>> - I am using DZVP-MOLOPT-SR-GTH for all atoms.
>> - I have added CHARGE 0 and MULTIPLICITY 2 ( I am not completely sure
>> about this but I have 55 atoms.).
>> - I have expanded the Cutoff as follows:
>>
>>  &MGRID
>>
>>       CUTOFF 400
>>
>>       REL_CUTOFF 60
>>
>>       NGRIDS 5
>>
>>     &END MGRID
>> I still have the same problem. I am worried because the Convergence of
>> the SCF optimisation up instead of decreasing.
>>
>>  Step     Update method      Time    Convergence         Total energy
>> Change
>>
>>
>> ------------------------------------------------------------------------------
>>
>>      1 P_Mix/Diag. 0.40E+00   25.1     1.97116897      -352.7972578538
>> -3.53E+02
>>
>>      2 P_Mix/Diag. 0.40E+00   22.1     1.15920278      -353.8713026582
>> -1.07E+00
>>
>>      3 P_Mix/Diag. 0.40E+00   22.5     0.70468277      -354.5020638040
>> -6.31E-01
>>
>>      4 P_Mix/Diag. 0.40E+00   22.5     1.81519648      -354.7042785765
>> -2.02E-01
>>
>>      5 P_Mix/Diag. 0.40E+00   22.6     1.40667909      -353.4830224789
>> 1.22E+00
>>
>>      6 P_Mix/Diag. 0.40E+00   22.6     1.61367789      -352.6169777702
>> 8.66E-01
>>
>>      7 P_Mix/Diag. 0.40E+00   22.8     9.77791081      -349.7222190083
>> 2.89E+00
>>
>>      8 P_Mix/Diag. 0.40E+00   22.7     3.04606642      -338.8207963019
>> 1.09E+01
>>
>>      9 P_Mix/Diag. 0.40E+00   22.9    10.99358257      -288.8580020934
>> 5.00E+01
>>
>>     10 P_Mix/Diag. 0.40E+00   22.9     5.98455238      -271.1871548265
>> 1.77E+01
>>
>> ...
>> And after this remains between 4 and 5 for a long time.
>>
>>
>> Thanks,
>>
>> Salome
>>
>> On Friday, 14 May 2021 at 13:03:25 UTC+2 pier... at gmail.com wrote:
>>
>>> Hi Salome,
>>>
>>>
>>>
>>> Two things come to my mind, first you should specify the charge and
>>> multiplicity of your system. Then, the cutoff and rel_cutoff might be too
>>> small.
>>>
>>>
>>>
>>> Actually, there’s a third: why mixing MOLOPT and MOLOPT-SR? Just go with
>>> the latter, they usually work fine.
>>>
>>>
>>>
>>> Regards,
>>>
>>> Pierre
>>>
>>>
>>>
>>> *From: *c... at googlegroups.com <c... at googlegroups.com> on behalf of
>>> salo... at gmail.com <salo... at gmail.com>
>>> *Date: *Friday, 14 May 2021 at 11:53
>>> *To: *cp2k <c... at googlegroups.com>
>>> *Subject: *[CP2K:15362] Problem converging SCF for a system containing
>>> Fe2+
>>>
>>> Dear all,
>>>
>>>
>>>
>>> I am quite new to CP2K and working with transition metals.
>>>
>>>
>>>
>>> I am trying to reproduce some results of an O2 molecule dissociating
>>> from an heme group (Fe2+). I am struggling to converge the SCF wavefunction
>>> even in a singlepoint calculation and I am not sure what I am doing wrong
>>> here.
>>>
>>>
>>>
>>> As an initial guess, I am using PBE with the following combination of
>>> basis sets and pseudopotentials:
>>>
>>> - Fe: BASIS_SET DZVP-MOLOPT-SR-GTH & GTH-PBE-q16.
>>>
>>> - All the other atoms: DZVP-MOLOPT-GTH with GTH-PBE-q* .
>>>
>>>
>>>
>>> I have attached the input file and the initial geometry.
>>>
>>>
>>>
>>> Can you help me out?
>>>
>>>
>>>
>>> Thank you very much in advance,
>>>
>>>
>>>
>>> Salome
>>>
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