[CP2K-user] [CP2K:19553] Re: Significant discontinuity in EOS curver for FeO

[Kejiang Li]

Dear Matthias,

Thanks a lot for providing this detailed tutorial for FeO. This will 
benefit a lot of CP2K users.

I have just done a fast test with your code, which produces very accurate 
results compared with my QE results (my spin direction is along 001, so 
this might cause a slight difference). See the attached figure.

I have also quickly compared your codes and my codes. I noticed the 
following main differences and have some quick questions:

1. You didn't set the VDW_POTENTIAL. Don't we need to 
consider VDW_POTENTIAL for FeO?

2. You didn't set the initial value for MAGNETIZATION. Is this also not 
necessary for FeO?

3. You didn't set the UKS and MULTIPLICITY. Is the default setting for UKS 
and MULTIPLICITY enough for FeO?

I think it might be due to one of the above reasons that caused the 
discontinuity in my EOS calculation. Anyway, I will do more tests to check 
the influence of the above factors.

Looking forward to hearing from you.

Thanks a lot for your kind help.

Best regards,
Kejiang
[image: matthias.png]


On Thursday, November 23, 2023 at 5:39:55 PM UTC+8 Krack Matthias wrote:

> Dear Kejiang
>
>  
>
> I have added a howto page <https://www.cp2k.org/howto:dft_u> to the CP2K 
> wiki for DFT+U calculations with an EOS calculation for cubic FeO as an 
> example.
>
>  
>
> HTH
>
>  
>
> Matthias
>
>  
>
> *From: *cp... at googlegroups.com <cp... at googlegroups.com> on behalf of 
> Kejiang Li <lyam_... at 126.com>
> *Date: *Wednesday, 22 November 2023 at 07:19
> *To: *cp2k <cp... at googlegroups.com>
> *Subject: *[CP2K:19547] Re: Significant discontinuity in EOS curver for 
> FeO
>
> Dear all, 
>
> Here, I also attached the test results with different sizes of supercells. 
> There is still a sharp decrease or discontinuity on the left side of the 
> lowest point.
>
> Could anyone provide any guidance?
>
> Thanks a lot.
>
> Best regards,
>
> Kejiang
>
> On Monday, November 20, 2023 at 9:00:11 AM UTC+8 Kejiang Li wrote:
>
> Dear CP2K community,
>
> I am calculating the EOS for FeO with a 2*2*2 supercell. But there is 
> always a significant discontinuity (sharp decrease) in the range of 4.3-4.4 
> angstrom lattice constant in the EOS curves, as shown in the figures below.
>
> I have done the following tests:
> - the convergence of the energy with different cutoffs;
> - using different functionals, including PBE, HSE, and SCAN;
> -including HSE with different HF fractions;
> -using different magnetization and +U settings. 
> However, all the tests produce similar results with an apparent 
> discontinuity (4.3-4.3 A) .
>
> This discontinuity is not observed in the Quantum Espresso results 
> conducted by myself and in the results of literature that generally used 
> VASP.  I believe that the CP2K program might cause this problem.
>
> Can you give me more suggestions on how to do further tests?
>
> Here, I also attached one sample code I used during my tests.
>
> Thanks a lot.
>
> Best regards,
> Kejiang
> The University of Science and Technology Beijing
>
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