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

[Timrov Iurii]

Dear Mona,


> "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."


In Abhirup's system, the DOS at the Fermi level does not seem to be small, as printed in the output:

DOS(E_Fermi) =    0.1303E+04

So it seems there are states at the Fermi level, and hence the code should work fine. I think it is really a problem of a wrong setup of the PWscf calculation.


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


What do you mean? The HP code is based on linear response theory, in the framework of the simplified rotationally-invariant scheme by Dudarev et al., PRB 57, 1505 (1998).


Cheers,

Iurii


--
Dr. Iurii Timrov
Postdoctoral Researcher
STI - IMX - THEOS and NCCR - MARVEL
Swiss Federal Institute of Technology Lausanne (EPFL)
CH-1015 Lausanne, Switzerland
+41 21 69 34 881
http://people.epfl.ch/265334
________________________________
From: users <users-bounces at lists.quantum-espresso.org> on behalf of Mona Asadinamin <Mona.a at uga.edu>
Sent: Monday, July 27, 2020 3:24:00 PM
To: Quantum ESPRESSO users Forum
Subject: Re: [QE-users] Problem with hp.x for f-metals

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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