[QE-users] Error with hp.x while calculating Hubbard U parameter

[Iurii TIMROV]

Dear Prof. Samir Ranjan Meher ,


The solution is already written in your email:


         The DOS at the Fermi level is too small:
         DOS(E_Fermi) =   -0.1639E-79
         This means that most likely the system has a gap,
         and hence it should NOT be treated as a metal


Therefore, please remove this from your input file:

> occupations = 'smearing', smearing = 'mv', degauss=0.001


In any case, if you use linear response theory to compute U for Zn-3d you will obtain a very large value. Check this paper: K. Yu and E.A. Carter, J. Chem. Phys. 140, 121105 (2014)


HTH


Iurii


--
Dr. Iurii TIMROV
Senior Research Scientist
Theory and Simulation of Materials (THEOS)
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 Samir Ranjan Meher <samirmeher at gmail.com>
Sent: Wednesday, November 3, 2021 4:01:43 PM
To: users at lists.quantum-espresso.org
Subject: [QE-users] Error with hp.x while calculating Hubbard U parameter

Hello everyone,

Greetings.

I am facing the following error while trying to obtain the "Hubbard-U" parameter for Zn in ZnO through linear response theory using hp.x.

 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) =   -0.1639E-79
         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...
STOP 1


The scf input file is as follows:
=======================================================
&control
    calculation = 'scf',
    prefix='zno',
    pseudo_dir = 'D:/Data/samir/qe/pseudo',
    outdir='D:/Data/samir/qe/ZnO/hp/tmp'
/
&system
  ibrav = 4, nat=4, ntyp= 2, a = 3.2494, c = 5.2038
  ecutwfc = 60, ecutrho = 300
  occupations = 'smearing', smearing = 'mv', degauss=0.001
  lda_plus_U=.TRUE.
  lda_plus_U_kind = 0,
  U_projection_type = 'ortho-atomic'
  Hubbard_U(1)=1.d-10
/

&ELECTRONS
  mixing_mode='plain'
  mixing_beta = 0.7,
  conv_thr =  1.0d-10,
/

ATOMIC_SPECIES
Zn     65.39000  Zn.pbesol-dnl-kjpaw_psl.1.0.0.UPF
O      15.99940  O.pbesol-n-kjpaw_psl.1.0.0.UPF

ATO&control
    calculation = 'scf',
    prefix='zno',
    pseudo_dir = 'D:/Data/samir/qe/pseudo',
    outdir='D:/Data/samir/qe/ZnO/hp/tmp'
/
&system
  ibrav = 4, nat=4, ntyp= 2, a = 3.2494, c = 5.2038
  ecutwfc = 60, ecutrho = 300
  occupations = 'smearing', smearing = 'mv', degauss=0.001
  lda_plus_U=.TRUE.
  lda_plus_U_kind = 0,
  U_projection_type = 'ortho-atomic'
  Hubbard_U(1)=1.d-10
/

&ELECTRONS
  mixing_mode='plain'
  mixing_beta = 0.7,
  conv_thr =  1.0d-10,
/

ATOMIC_SPECIES
Zn     65.39000  Zn.pbesol-dnl-kjpaw_psl.1.0.0.UPF
O      15.99940  O.pbesol-n-kjpaw_psl.1.0.0.UPF

ATOMIC_POSITIONS {angstrom}
Zn     -0.000016   1.876051   0.000000
Zn      1.624700   0.938040   2.601900
O      -0.000016   1.876051   1.988372
O       1.624700   0.938040   4.590272

K_POINTS {automatic}
 8 8 4  0 0 0
=================================================================

Can anybody suggest any solution to this?

Thank you,
Best wishes
Samir Ranjan Meher
Assistant Professor
Department of Physics
School of Advanced Sciences
Vellore Institute of Technology, Vellore
Tamilnadu- 632014
India
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