[CP2K-user] [CP2K:19835] DFT+U warnings

[Krack Matthias]

Hi Dhananjay

The warning is caused by shell occupations larger than the physically accepted value, e.g. a total of more than 10 electrons in a 3d shell. The Mulliken population analysis can give such occupations and the warning hints to check the actual occupations. The warning can be ignored if the occupations are only slightly larger than the expected maximal value, e.g. 10.3 instead of 10.0 for 3d.


  1.  CP2K requires usually much smaller U values than plane waves codes like VASP for a similar effect on the band gap and structural parameters. I suggest to try roughly half the U value, i.e. 2 eV for Mn, first.
  2.  DFT+U is not yet implemented with k points in CP2K which implies that you will have to employ sufficiently large simulation cells.

Your system/setup is too small and does not converge at all and the resulting orbital occupations are useless which explains the warning.
I suggest to try OT without smearing instead of Broyden diagonalization first for at least 3x3x3 unit cells.

HTH

Matthias

From: cp2k at googlegroups.com <cp2k at googlegroups.com> on behalf of Gupta Dhananjay <guptadhananjay7645 at gmail.com>
Date: Monday, 29 January 2024 at 09:35
To: cp2k at googlegroups.com <cp2k at googlegroups.com>
Subject: [CP2K:19831] DFT+U warnings
Dear cp2k developers and users,
I am running AIMD NPT equilibration for Na2Mn3O7. I am getting the warning:
"DFT+U energy contibution is negative ***
 *** possibly due to unphysical Mulliken charges"

In addition, I have the following doubts:
1. I have used U=3.9 eV for Mn as per literature (but, the package used for that was VASP), is it ok to use with cp2k code ?
2. Is it possible to use k-points instead of gamma-point while using DFT+U ?

Find the attached input  and output file.
Please give the comments.
Thank you so much !!

--
Regards
Dhananjay
---------------------------------------------------
Dhananjay
Research Scholar
Department of Chemistry | CCMB-Lab
Indian Institute of Technology Delhi
Hauz Khas, New Delhi-110016, India
Phone: +916299276960
Email: cyz228301 at iitd.ac.in<http://iitd.ac.in>
Web: https://guptadhananjay7645.wixsite.com/djay-chem


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