[CP2K-user] [CP2K:14845] Re: Energy Fluctuations in Geometry Optimization

[Tim Wang]

Dear Fabian and Lenard,

Thank you for your suggestions! I'll try that to get a more reasonable structure first.

Best regards,
Xiao Wang

________________________________
From: cp... at googlegroups.com <cp... at googlegroups.com> on behalf of fa... at gmail.com <fabia... at gmail.com>
Sent: Monday, March 1, 2021 6:59 PM
To: cp2k <cp... at googlegroups.com>
Subject: [CP2K:14845] Re: Energy Fluctuations in Geometry Optimization

Hi Xiao,

As Lenard pointed out your SCF does not converge, consequently the forces are not converged and BFGS cannot optimize the structure.
You should adjust a few parameters:
MAX_SCF 200 ! change if needed to make sure SCF is really converged
ELECTRONIC_TEMPERATURE     2000 ! large smearing helps convergence. If needed you can reduce this once the optimization is converged and restart
ALPHA 0.01 !  you can play with this but it probably needs to be << 0.1

To speed up the first few steps of geometry optimization you could consider reducing the k-point grid to something like

    SCHEME  MONKHORST-PACK  2  3  1
    !FULL_GRID  .TRUE.

Once the the geometry is more reasonable you can switch back the the more accurate k-point sampling.

Cheers,
Fabian
On Sunday, 28 February 2021 at 20:36:45 UTC+1 ASSIDUO Network wrote:
If I'm not mistaken, I think your structure is too far away from the optimized geometry. Your best bet would probably be to get the best structure possible before starting the geometry optimization.

This is true because I see the following in your output file:
At the 50th cycle your convergence criterion is around 0.9, nowhere near 1.0E-07, and you also get a message of "SCF run NOT converged".

I don't really see any issues with the flags you chose, so I think your issue is probably with the structure. The same thing happened to me the other day.
On Saturday, February 27, 2021 at 7:15:49 PM UTC+2 ti... at hotmail.com wrote:
Dear CP2K Users,


I'm trying to run a geometry optimization for CoF2 (110) slabs, but the energy does not seem to decrease. Instead, it fluctuates a lot and sometimes increases significantly. I already used BFGS as the optimizer, and the eps_scf was set to 10^(-7). I'm wondering if anyone knows how to deal with such a problem. My input file, the generated xyz file, and the output file are attached below.

Thanks in advance!


Best regards,
Xiao

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