[CP2K-user] [CP2K:19559] Re: Significant discontinuity in EOS curver for FeO

[Krack Matthias]

Dear Kejiang

  *   1. You didn't set the VDW_POTENTIAL. Don't we need to consider VDW_POTENTIAL for FeO?
Not sure if that is needed for bulk FeO. Did you check the work of other authors? Did they apply such a vdW correction for bulk FeO?

  *   2. You didn't set the initial value for MAGNETIZATION. Is this also not necessary for FeO?
The &BS section does the same, i.e. sets the initial on-site electronic configuration for the iron atoms, and it allows for a more detailed control.

  *   3. You didn't set the UKS and MULTIPLICITY. Is the default setting for UKS and MULTIPLICITY enough for FeO?
Yes, it is for AFM FeO as I already explained.
Matthias
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[https://groups.google.com/group/cp2k/attach/c32459892868/cell.jpg?part=0.1&view=1]
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
Error! Filename not specified.
Error! Filename not specified.Error! Filename not specified.
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