Hi,
Fermi energy is not really defined in an insulator/semiconductor; at 0
temperature any value in the gap a is good fermi energy, but better to
talk about the chemical potential. At temperature is raised, it would be
approximately start in the middle of the gap, and move away from that
depending on how the conduction and valence DOS are. Maybe read the
Ashcroft Mermin chapter on homogeneous semiconductors (27, I think).
A typical good choice for smearing (0.02 Ry, 0.15 A^-1 density of
k-points) would give you the fermi energy in the middle of the gap,
approximately, if you use gaussian smearing in an insulator. mv and mp
should not be used for an insulator/semiconductor.
Also, mv has positive occupations, so something seems wrong with your
plot - are you sure you are not using mp?
nicola
On 27/06/2020 14:56, 후신 부지드 wrote:
Dear QE users,
I tried to search a solution for this problem and looked to the previous
posts but didn't work with me
I made scf calculation for bulk SnS2 with dft-d3 using occupations=
'tetrahedra' I get the the fermi level Ef on top of the valence band as
reported in the literature,
but when I try to use smearing the Ef will shifts about 1 eV to locate
in the middle of the gap
I tried gaussian smearing and fd using a huge k points, but eventhough
the energy converges to the value in tertahedra case, the Ef always
shifts by ~ 1eV.
The only exception is mv smearing with 0.01 degauss it gives the right
Ef, (but it has a tail with finite dos which is not seen in the gaussian
case with wrong Ef, pls see the attached image) and when I try mv with
0.005 degauss it also show wrong Ef even with huge k points.
Does anyone know why I'm getting this shift in Ef even though the energy
is converged and the kpoint is large enough
Here is the input file for tetrahedra and smearing:
Tetrahedra:
&control
calculation = 'scf'
restart_mode='from_scratch'
prefix = 'tet'
outdir = '/home/outdir'
pseudo_dir = '/home/pseudo'
verbosity = 'high'
/
&system
ibrav = 0,
nat = 6,
ntyp = 2,
ecutwfc=80
ecutrho=560
vdw_corr = 'dft-d3'
occupations='tetrahedra'
nbnd=52
lda_plus_u=.true.
Hubbard_U(1)=9.0,
Hubbard_U(2)=9.0,
/
&electrons
conv_thr=1e-6
/
ATOMIC_SPECIES
Sn 118.71000 Sn.pbe-dn-kjpaw_psl.1.0.0.UPF
S 32.06600 S.pbe-n-kjpaw_psl.1.0.0.UPF
ATOMIC_POSITIONS (angstrom)
Sn -0.000001900 2.129228760 7.368473930
Sn 1.843967305 1.064612836 1.474204489
S 1.843967305 1.064612836 8.846101191
S -0.000001900 2.129228760 2.951831855
S -0.000000000 -0.000000000 -0.005322640
S -0.000000000 0.000000000 5.888946695
CELL_PARAMETERS (angstrom)
3.687930810 0.000000000 -0.000000000
-1.843965405 3.193841769 -0.000000000
-0.000000000 -0.000000000 11.788538670
K_POINTS (automatic)
20 20 6 0 0 0
Smearing
&control
calculation = 'scf'
restart_mode='from_scratch'
prefix = 'smea'
outdir = '/home/outdir'
pseudo_dir = '/home/pseudo'
verbosity = 'high'
/
&system
ibrav = 0,
nat = 6,
ntyp = 2,
ecutwfc=80
ecutrho=560
vdw_corr = 'dft-d3'
occupations='smearing',smearing='gaussian',degauss=0.01
lda_plus_u=.true.
Hubbard_U(1)=9.0,
Hubbard_U(2)=9.0,
/
&electrons
conv_thr=1e-6
/
ATOMIC_SPECIES
Sn 118.71000 Sn.pbe-dn-kjpaw_psl.1.0.0.UPF
S 32.06600 S.pbe-n-kjpaw_psl.1.0.0.UPF
ATOMIC_POSITIONS (angstrom)
Sn -0.000001900 2.129228760 7.368473930
Sn 1.843967305 1.064612836 1.474204489
S 1.843967305 1.064612836 8.846101191
S -0.000001900 2.129228760 2.951831855
S -0.000000000 -0.000000000 -0.005322640
S -0.000000000 0.000000000 5.888946695
CELL_PARAMETERS (angstrom)
3.687930810 0.000000000 -0.000000000
-1.843965405 3.193841769 -0.000000000
-0.000000000 -0.000000000 11.788538670
K_POINTS (automatic)
32 32 10 0 0 0
Houcine BOUZID
Sungkyunkwan University,
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--
----------------------------------------------------------------------
Prof Nicola Marzari, Chair of Theory and Simulation of Materials, EPFL
Director, National Centre for Competence in Research NCCR MARVEL, EPFL
http://theossrv1.epfl.ch/Main/Contact http://nccr-marvel.ch/en/project
_______________________________________________
Quantum ESPRESSO is supported by MaX (www.max-centre.eu/quantum-espresso)
users mailing list users@lists.quantum-espresso.org
https://lists.quantum-espresso.org/mailman/listinfo/users
