Smooth GW band structure

[burkzdemir]

Dear developers,

I obtained the GW energies and interpolated them along high symmetry points with ypp to obtain the band structure. However, the GW band structure is not smooth enough for a publication quality. How can I get rid of the discontinuities and make it more smooth?

Best,
Burak

[Daniele Varsano]

Dear Burak,
probably the best option is to perform a Wannier interpolation.
Here you can find a tutorial/example for the that using Wannier90 with yambo QP energies:
viewtopic.php?f=9&t=1661&p=11005&hilit=wannier#p11005

Best,
Daniele

[Sumit]

Dear Developers,

I followed the example in the wiki "GW parallel strategies" to compute the band structure of hBN-2D. I got plot with discreteness means no continuity

s.pdf

. Can you please suggest to me what may go wrong?
Additionally, I found the above link to interpolate using wannier90 but no workflow is given there. Is any other tutorial section is available with wannier90 and Yambo to use?

Thank You!

Regards
Sumit Kukreti
Ph.D. Scholar
IIT Jodhpur INDIA

[Daniele Varsano]

Dear Sumit,
what interpolation mode are you using in ypp input?
you can try to use the BOLTZ algorithm for interpolation:
INTERP_mode= "BOLTZ"


In this thread, you can find an example and tutorial to use wannier90.
viewtopic.php?p=11005#p11005

Best,
Daniele

[burkzdemir]

Dear developers,

I solved the smoothness problem by switching NN to BOLTZ. But now, I have another problem. The GW band gap I obtain for uniform grid without interpolation is 1.6 eV which drops down to 1.0 eV after interpolation. But, GW values for this material in the literature is 1.7 eV and experimental gap is 1.8 eV. So, the GW gap for the uniform grid seems ok but after interpolation it drops down too much. I don't understand the problem here. Here are my input files.

-------------------------yambo.in--------------------------------------------------------------------------
gw0 # [R] GW approximation
ppa # [R][Xp] Plasmon Pole Approximation for the Screened Interaction
dyson # [R] Dyson Equation solver
HF_and_locXC # [R] Hartree-Fock
em1d # [R][X] Dynamically Screened Interaction
NLogCPUs=0 # [PARALLEL] Live-timing CPU`s (0 for all)
PAR_def_mode= "memory" # [PARALLEL] Default distribution mode ("balanced"/"memory"/"workload")
EXXRLvcs= 304205 RL # [XX] Exchange RL components
VXCRLvcs= 304205 RL # [XC] XCpotential RL components
Chimod= "HARTREE" # [X] IP/Hartree/ALDA/LRC/PF/BSfxc
% BndsRnXp
1 | 80 | # [Xp] Polarization function bands
%
NGsBlkXp= 13 Ry # [Xp] Response block size
% LongDrXp
1.000000 | 0.000000 | 0.000000 | # [Xp] [cc] Electric Field
%
PPAPntXp= 27.21138 eV # [Xp] PPA imaginary energy
XTermKind= "BG" # [X] X terminator ("none","BG" Bruneval-Gonze)
% GbndRnge
1 | 80 | # [GW] G[W] bands range
%
GTermKind= "BG" # [GW] GW terminator ("none","BG" Bruneval-Gonze,"BRS" Berger-Reining-Sottile)
DysSolver= "n" # [GW] Dyson Equation solver ("n","s","g")
GWoIter=0 # [GW] GWo self-consistent (evGWo) iterations on eigenvalues
GWIter=0 # [GW] GW self-consistent (evGW) iterations on eigenvalues
%QPkrange # [GW] QP generalized Kpoint/Band indices
1|452|7|12|
%
-----------------ypp.in------------------------
electrons # [R] Electronic properties
bnds # [R] Bands
PROJECT_mode= "none" # Instruct ypp how to project the DOS. ATOM, LINE, PLANE.
INTERP_mode= "BOLTZ" # Interpolation mode (NN=nearest point, BOLTZ=boltztrap aproach)
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= 0.000000 # [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
% BANDS_bands
7 | 12 | # Number of bands
%
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_steps= 30 # Number of divisions
#BANDS_built_in # Print the bands of the generating points of the circuit using the nearest internal point
%BANDS_kpts # K points of the bands circuit
0.0000000000 | 0.0000000000 | 0.5000000000 |
0.0000000000 | 0.0000000000 | 0.0000000000 |
0.6666700000 | -0.3333300000 | 0.5000000000 |
0.0000000000 | 0.0000000000 | 0.5000000000 |
0.5000000000 | -0.5000000000 | 0.5000000000 |
0.6666700000 | -0.3333300000 | 0.5000000000 |
0.6666700000 | -0.3333300000 | 0.0000000000 |
0.0000000000 | 0.0000000000 | 0.0000000000 |
0.5000000000 | -0.5000000000 | 0.0000000000 |
0.6666700000 | -0.3333300000 | 0.0000000000 |
%

[Daniele Varsano]

Dear Burak,
can you show a plot of the band structure containing interpolated and calculated points?

Best,
Daniele

[burkzdemir]

But they are on different k paths. How can I draw both in the same graph?

Best,

[Daniele Varsano]

Dear Burak,
I imagine some of the k points of the regular grid are contained in the path. Looking at this you can check if the interpolation is working properly.
Best,
Daniele