[QE-users] Problem with hp.x for f-metals

[Mona Asadinamin]

Dear Abhirup;

I have faced the same problem, but for a magnetic insulator; However the nature of the problem is similar.

Please see example 02 in QE for hp.x :

"When you use linear response theory to determine U, in DFPT there is a metallic correction at q=0 that is proportional to the inverse of DOS at the Fermi level. (Rev. Mod. Phys. 73, 515 (2001)) and if the Fermi level is too small, the Fermi energy shift in DFPT will be very large."

I would say you can try to find the U parameter using rotationally invariant scheme instead.

Best regards;

Mona Asadi Namin
Graduate student
Center for simulational physics
University of Georgia
--------------------------------------
Email:mona.a at uga.ed<mailto:mona.a at uga.edu>u<mailto:mona.a at uga.edu>
Phone: +1-215-906-23-92


________________________________
From: users <users-bounces at lists.quantum-espresso.org> on behalf of Abhirup Patra <abhirupp at sas.upenn.edu>
Sent: Saturday, July 25, 2020 12:20 AM
To: Quantum ESPRESSO users Forum <users at lists.quantum-espresso.org>
Subject: [QE-users] Problem with hp.x for f-metals

[EXTERNAL SENDER - PROCEED CAUTIOUSLY]

Hello,

I am trying to compute Hubbard U using hp.x for Cerium, however, it seems that after few iterations the code stopped with the following message:

     atom #  1   q point #   1   iter # 395
      Fermi energy shift (Ry) = -0.5530E+01 -0.2375E-07

      WARNING: The Fermi energy shift is too big!
      This may happen in two cases:
      1. The DOS at the Fermi level is too small:
         DOS(E_Fermi) =    0.1303E+04
         This means that most likely the system has a gap,
         and hence it should NOT be treated as a metal
         (otherwise numerical instabilities will appear).
      2. Numerical instabilities due to too low cutoff
         for hard pseudopotentials.

      Stopping...

Any help would be appreciated.

Best,
Abhirup

----------------------------------------------------------------------------------------------
Abhirup Patra
Postdoctoral Research Fellow
Department of Chemistry
University of Pennsylvania
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