[CP2K-user] [CP2K:19737] Ground state convergance issues

[Ava Rajh]

Dear  Augustin,

Thank you very much for your input. My cell is quite small in z direction,
that's why I had to set the  cutoff radius to 2 (or 1.5). I will try to
increase the vertical size of the system and repeat the calculation.
I will also try other performance optimizations you suggested, and change
the basis set.

Thynk you for the suggestions,
kind regards, Ava


V V pet., 12. jan. 2024 ob 17:33 je oseba Augustin Bussy <
augustin.bussy at chem.uzh.ch> napisala:

> Dear Ava,
>
> you are correct, your issue most likely comes from your Hartree-Fock
> input. You are using a cutoff radius of 1.5 Ang for the truncated Coulomb
> potential. This is very small and might  lead to inaccuracies in the
> electronic structure. Typically, calculations are run with a truncation
> radius of 5-6 Ang. Note that the sphere with the same radius should fit in
> your simulation cell: you might need to increase the size of the system to
> fit such a large truncation radius.
>
> In terms of performance, you are using an extremely tight EPS_PGF_ORB
> value. This will lead to very slow calculations. The default of 1.0E-5 is
> usually enough, and 1.0E-6 is already considered very accurate. On the
> other hand, EPS_SCHWARZ = 1.0E-6 is fairly loose. Using 1.0E-8 might help
> with numerical stability. If you are going to run a larger system, you will
> probably need to tweak the HF%MEMORY%MAX_MEMORY value for optimal runtime.
>
> You can also try to use the more modern ADMM basis set defined in the
> BASIS_ADMM_UZH data file.
>
> Best,
> Augustin
> ------------------------------
> *From:* cp2k at googlegroups.com <cp2k at googlegroups.com> on behalf of Ava
> Rajh <ava.rajh at gmail.com>
> *Sent:* Friday, January 12, 2024 11:34 AM
> *To:* cp2k <cp2k at googlegroups.com>
> *Subject:* [CP2K:19733] Ground state convergance issues
>
> Hi all,
>
> I am trying to compare some ground state XAS and TDDFT XAS for a few
> systems and it was going great on other systems until I started on a
> relatively simple graphite cell.
> I performed cell optimization and used the resulting structure of 64 C
> atoms for XAS calculation but i am having issues with ground state
> calculation of a system which would be compatible with further TDDFT,. SCF
> does not seem to converge and either diverges wildly or oscillates around
> 0.
>
> I have included a sample input file, I have tried also with the DIIS OT,
> denationalization, and with a PBE functional but the issue persist. I am
> hoping someone might have an idea if I missed something obvious. It seems
> that the problem might be in the HF part, as the convergence is slightly
> better if I change the HF fraction, but it ultimately always diverges.
>
> I would be grateful f anyone has any comments on the issue I am facing and
> I apologize if I missed something obvious.
> kind regards, Ava
>
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