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Fermi level adjustment
Posted: Thu Apr 14, 2022 7:10 pm
by hammouri
Hello all,
When I graph the band structure with DFT I see the valance band max located at zero. But when I try the band structure with GW, I see the valance band max located below zero. In the Hartree output, the max of VB is -6.866995 eV whereas the Ef is 7.889769 eV so the difference is about 1.02 eV. This shift put the BS above the zero, see the attached pic.
Code: Select all
[X] === General ===
[X] Electronic Temperature : 0.000000 0.000000 [eV K]
[X] Bosonic Temperature : 0.000000 0.000000 [eV K]
[X] Finite Temperature mode : no
[X] El. density : 0.95891E+24 [cm-3]
[X] Fermi Level : 7.889769 [eV]
[X] === Gaps and Widths ===
[X] Conduction Band Min : 1.590475 [eV]
[X] Valence Band Max : 0.000000 [eV]
[X] Filled Bands : 30
[X] Empty Bands : 31 100
[X] Direct Gap : 2.479373 [eV]
[X] Direct Gap localized at k-point : 1
[X] Indirect Gap : 1.590475 [eV]
[X] Indirect Gap between k-points : 80 1
[X] Last valence band width : 0.888898 [eV]
[X] 1st conduction band width : 3.874326 [eV]
Code: Select all
[06.01] Hartree-Fock occupations report
=======================================
[Hartree-Fock] === General ===
[Hartree-Fock] Electronic Temperature : 0.000000 0.000000 [eV K]
[Hartree-Fock] Bosonic Temperature : 0.000000 0.000000 [eV K]
[Hartree-Fock] Finite Temperature mode : no
[Hartree-Fock] El. density : 0.95891E+24 [cm-3]
[Hartree-Fock] Fermi Level : 7.889769 [eV]
[Hartree-Fock] === Gaps and Widths ===
[Hartree-Fock] Conduction Band Min : 5.823715 [eV]
[Hartree-Fock] Valence Band Max : -6.866995 [eV]
[Hartree-Fock] Filled Bands : 30
[Hartree-Fock] Empty Bands : 31 100
[Hartree-Fock] Direct Gap : 13.30329 [eV]
[Hartree-Fock] Direct Gap localized at k-point : 1
[Hartree-Fock] Indirect Gap : 12.69071 [eV]
[Hartree-Fock] Indirect Gap between k-points : 7 1
[Hartree-Fock] Last valence band width : 0.913032 [eV]
[Hartree-Fock] 1st conduction band width : 4.944641 [eV]
Re: Fermi level adjustment
Posted: Mon Apr 18, 2022 9:48 am
by Daniele Varsano
Dear Hammouri,
Yambo by default sets the zero energy as the valence band maximum of the KS structure. All the corrections are done considering this value as zero.
Next the Fermi energy of the QE calculation (ie the operated shift is reported).
Note that the HF occupation report is meaningful only if you calculate corrections for all the k points.
Best,
Daniele
Re: Fermi level adjustment
Posted: Tue Apr 19, 2022 11:17 am
by hammouri
Daniele Varsano wrote: ↑Mon Apr 18, 2022 9:48 am
Note that the HF occupation report is meaningful only if you calculate corrections for all the k points.
Well, the HF occupation report I posted above is actually done for all the k points. I shifted the valance band by -6.866995 eV but it did not locate at zero as seen from the band structure I included above.
Re: Fermi level adjustment
Posted: Tue Apr 19, 2022 3:03 pm
by Daniele Varsano
Dear Hammouri,
the plot you posted is a GW or HF band structure?
eventually, can you post your input/output/reports of the GW calculation and interpolation?
Daniele
Re: Fermi level adjustment
Posted: Tue Apr 19, 2022 5:38 pm
by hammouri
I am following the steps in this tutorial
http://www.yambo-code.org/wiki/index.ph ... rial:_h-BN. The band structure in that tutorial do not include any HF. Anyways, I posted the GW band structure.
These are the inputs:
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#
# __ __ _ __ __ ____ U ___ u
# \ \ / / U /"\ U u |" \/ "| u U | __") u \/"_ \/
# \ V / \/ _ \/ \| |\/| |/ \| _ \/ | | | |
# U_|"|_u / ___ \ | | | | | |_) | .-,_| |_| |
# |_| /_/ \_\ |_| |_| |____/ \_)-\___/
# .-,//|(_ \\ >> <<,-,,-. _|| \\_ \\
# \_) (__) (__) (__) (./ \.) (__) (__) (__)
#
#
# Version 5.0.4 Revision 19595 Hash 896bffc02
# Branch is
# MPI+HDF5_IO Build
# http://www.yambo-code.org
#
HF_and_locXC # [R] Hartree-Fock
ppa # [R Xp] Plasmon Pole Approximation
gw0 # [R] GW approximation
em1d # [R][X] Dynamically Screened Interaction
EXXRLvcs= 60 Ry # [XX] Exchange RL components
VXCRLvcs= 26745 RL # [XC] XCpotential RL components
Chimod= "HARTREE" # [X] IP/Hartree/ALDA/LRC/PF/BSfxc
% BndsRnXp
1 | 80 | # [Xp] Polarization function bands
%
NGsBlkXp= 4 Ry # [Xp] Response block size
% LongDrXp
1.000000 | 1.000000 | 1.000000 | # [Xp] [cc] Electric Field
%
PPAPntXp= 27.21138 eV # [Xp] PPA imaginary energy
XTermKind= "none" # [X] X terminator ("none","BG" Bruneval-Gonze)
% GbndRnge
1 | 50 | # [GW] G[W] bands range
%
GDamping= 0.10000 eV # [GW] G[W] damping
dScStep= 0.10000 eV # [GW] Energy step to evaluate Z factors
DysSolver= "n" # [GW] Dyson Equation solver ("n","s","g")
%QPkrange # [GW] QP generalized Kpoint/Band indices
1|84|25|36|
%
and this is the interpolation:
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# __ __ _ __ __ ____ U ___ u
# \ \ / / U /"\ U u |" \/ "| u U | __") u \/"_ \/
# \ V / \/ _ \/ \| |\/| |/ \| _ \/ | | | |
# U_|"|_u / ___ \ | | | | | |_) | .-,_| |_| |
# |_| /_/ \_\ |_| |_| |____/ \_)-\___/
# .-,//|(_ \\ >> <<,-,,-. _|| \\_ \\
# \_) (__) (__) (__) (./ \.) (__) (__) (__)
#
#
# Version 5.0.4 Revision 19595 Hash 896bffc02
# Branch is
# MPI+HDF5_IO Build
# http://www.yambo-code.org
#
electrons # [R] Electronic properties
bnds # [R] Bands
INTERP_Shell_Fac= 20.00000 # The bigger it is a higher number of shells is used
INTERP_NofNN= 1 # Number of Nearest sites in the NN method
OutputAlat= 7.5 # [a.u.] Lattice constant used for "alat" ouput format
cooIn= "rlu" # Points coordinates (in) cc/rlu/iku/alat
cooOut= "rlu" # Points coordinates (out) cc/rlu/iku/alat
#GfnQPdb="E < all_Bz/ndb.QP uei"
INTERP_mode= "BOLTZ" # Interpolation mode (NN=nearest point, BOLTZ=boltztrap aproach)
BANDS_steps=20
% BANDS_bands
25 | 40 | # Number of bands
%
%BANDS_kpts # K points of the bands circuit
0.500 |0.500 |0.500
0.000 |0.000 |0.000
0.000 |0.500 |0.000
0.500 |0.500 |0.000
0.000 |0.000 |0.000
%
CIRCUIT_E_DB_path= "none" # SAVE obtained from the QE `bands` run (alternative to %BANDS_kpts)
BANDS_path= "" # High-Symmetry points labels (G,M,K,L...) also using composed positions (0.5xY+0.5xL).
%BANDS_kpts # K points of the bands circuit
%
~
r-all_Bz_HF_and_locXC_gw0_em1d_ppa.txt
r_ypp.txt
o-all_Bz.qp.txt
Re: Fermi level adjustment
Posted: Tue Apr 19, 2022 9:23 pm
by claudio
Dear Hammouri
when you calculate the GW correction to the band structure Yambo do not automatically recalculate the Fermi energy,
and therefore the top of the valence bands in the GW band structure is not zero.
You can shift it by hand in your plot.
The same problem appear if you interpolate the GW band structure.
However, if you use the quasi-particle band structure in other calculations as BSE etc... in this case Yambo will put the top valence bands at zero.
best regards
Claudio
Re: Fermi level adjustment
Posted: Wed Apr 20, 2022 1:00 am
by hammouri
Thank you claudio for your reply!
I did it by hand, I mean I added 6.866995 eV to all energies to set the max valance band at zero. But as you see in the band structure graph, the max valance band is above zero.
Re: Fermi level adjustment
Posted: Wed Apr 20, 2022 8:59 am
by claudio
Dear Hammouri,
try to make a test.
Use the quasi-particle band structure you calculated to get the optical absorption by doing:
yambo -o c -V qp
and read the quasi-particles
XfnQPdb= "E < SAVE/ndb.QP" # [EXTQP Xd] Database action
run the calculations and in the report file you will find the correct Fermi energy for the GW quasi-particle
best
Claudio
Re: Fermi level adjustment
Posted: Wed Apr 20, 2022 9:36 am
by Daniele Varsano
Dear Hammouri,
if you shift by the HF correction and not the GW correction you cannot get zero. Of course, the HF correction is much larger, you should shift by the obtained GW correction.
Best,
Daniele