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

[Timrov Iurii]

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> on behalf of Yin-Ying Ting <y.ting at fz-juelich.de>
Sent: Wednesday, January 24, 2024 17:09
To: users at lists.quantum-espresso.org <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



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