[QE-users] Hubbard U Parameters in pmw.x

[Yin-Ying Ting]

Dear Iurii and Mahmoud,


Thank you for your previous response. I have a follow-up question regarding the impact of using different Hubbard U values in the initial SCF calculation. Specifically, if a U value of 4.6 eV is used instead of 0.001 eV:

  1.  How does it affect the electronic structure and energy calculations?
  2.  What are the implications for the convergence and computational efficiency?
  3.  Does it influence the accuracy of Wannier functions and subsequent property predictions (such as band gap)?

I appreciate your insights on these points.


Best regards,

Yin-Ying Ting

PhD Student in Forschungszentrum Jülich



On 26.01.24 10:16, Timrov Iurii wrote:
Dear Yin-Ying,

> Why is it not recommended or feasible to employ the Hubbard U parameters right from the first SCF calculation?

It is feasible, you can do that. QE contains just one example with starting U=0.001, but you can use any value.

The pmw.x codes reads the Kohn-Sham wavefunctions (which can be DFT or DFT+U), and then builds Wannier functions. Note that these are not maximally localized. In the future releases of QE there will be a possibility to use maximally localized Wannier functions from Wannier90 for DFT+U calculations (we are working on that).

HTH

Iurii

----------------------------------------------------------
Dr. Iurii TIMROV
Tenure-track scientist
Laboratory for Materials Simulations (LMS)
Paul Scherrer Institut (PSI)
CH-5232 Villigen, Switzerland
+41 56 310 62 14
https://www.psi.ch/en/lms/people/iurii-timrov
________________________________
From: users <users-bounces at lists.quantum-espresso.org><mailto:users-bounces at lists.quantum-espresso.org> on behalf of Yin-Ying Ting <y.ting at fz-juelich.de><mailto:y.ting at fz-juelich.de>
Sent: Wednesday, January 24, 2024 17:09
To: users at lists.quantum-espresso.org<mailto:users at lists.quantum-espresso.org> <users at lists.quantum-espresso.org><mailto:users at lists.quantum-espresso.org>
Subject: [QE-users] Hubbard U Parameters in pmw.x

Dear Quantum Espresso Community,

I am currently working with the poormanwannier.x (pmw.x) as demonstrated
in example05 of PP. In this example, the procedure begins with a
self-consistent field (SCF) calculation without the incorporation of
Wannier functions (wf) and with very small Hubbard parameters (around
0.001). This is followed by the execution of pmw.x and a subsequent
second SCF calculation, this time including Wannier functions and the
Hubbard U parameters.

My question pertains to the rationale behind this two-step SCF
calculation approach, particularly concerning the Hubbard U parameters.
Why is it not recommended or feasible to employ the Hubbard U parameters
right from the first SCF calculation? Understanding the underlying
reasoning for this process would greatly enhance my comprehension of the
method and its applications.

I appreciate any insights or explanations you can provide. Thank you for
your time and assistance.

Best regards,

PhD student in Forschungszentrum Jülich

Yin-Ying Ting

--

Forschungszentrum Jülich GmbH
Institute of Energy and Climate Research
Theory and Computation of Energy Materials (IEK-13)
E-mail: y.ting at fz-juelich.de<mailto:y.ting at fz-juelich.de>



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Forschungszentrum Jülich GmbH
52425 Jülich
Sitz der Gesellschaft: Jülich
Eingetragen im Handelsregister des Amtsgerichts Düren Nr. HR B 3498
Vorsitzender des Aufsichtsrats: MinDir Stefan Müller
Geschäftsführung: Prof. Dr. Astrid Lambrecht (Vorsitzende),
Karsten Beneke (stellv. Vorsitzender), Dr. Ir. Pieter Jansens
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_______________________________________________
The Quantum ESPRESSO community stands by the Ukrainian
people and expresses its concerns about the devastating
effects that the Russian military offensive has on their
country and on the free and peaceful scientific, cultural,
and economic cooperation amongst peoples
_______________________________________________
Quantum ESPRESSO is supported by MaX (www.max-centre.eu<http://www.max-centre.eu>)
users mailing list users at lists.quantum-espresso.org<mailto:users at lists.quantum-espresso.org>
https://lists.quantum-espresso.org/mailman/listinfo/users

--

Forschungszentrum Jülich GmbH
Institute of Energy and Climate Research
Theory and Computation of Energy Materials (IEK-13)
E-mail: y.ting at fz-juelich.de<mailto:y.ting at fz-juelich.de>


------------------------------------------------------------------------------------------------
------------------------------------------------------------------------------------------------
Forschungszentrum Jülich GmbH
52425 Jülich
Sitz der Gesellschaft: Jülich
Eingetragen im Handelsregister des Amtsgerichts Düren Nr. HR B 3498
Vorsitzender des Aufsichtsrats: MinDir Stefan Müller
Geschäftsführung: Prof. Dr. Astrid Lambrecht (Vorsitzende),
Karsten Beneke (stellv. Vorsitzender), Dr. Ir. Pieter Jansens
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