Hi all,
probably this has been discussed before, although I could not find anything in the search, so I apologize in advance.
I need to determine the band structure of a thin film system, and have done the usual steps (QE scf, then nscf calculations at the special points, GW at the special points). As I understand, I am supposed to generate the band structure along high symmetry lines with ypp. So my first check was to compare the interpolated DFT band structure to the explicit one obtained with QE. The agreement is very bad though and changing some parameters in the ypp input file did not really help.
Is there an idea of what the issue could be? My guess is that the number of special k-points is too small to start from?
If the interpolation remains problematic: is there also a way to evaluate the QP corrections along the band structure path explicitly?
Thanks,
Bjoern
Explicit band structure vs interpolation
Moderators: Davide Sangalli, andrea.ferretti, myrta gruning, andrea marini, Daniele Varsano
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Explicit band structure vs interpolation
Bjoern Baumeier
TU Eindhoven
TU Eindhoven
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OnlineDaniele Varsano
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Re: Explicit band structure vs interpolation
Dear Bjoern,
Another way to perform interpolations (also considering GW energies) that should be more accurate is to go through Wannier90 interpolation.
Here you can find an example of how to interface Wannier90 and Yambo:
https://github.com/wannier-developers/w ... /example23
https://github.com/wannier-developers/w ... c/tutorial
Best,
Daniele
Yes, this could be an option, if your k point grid is too coarse this can bring inaccurate results.Is there an idea of what the issue could be? My guess is that the number of special k-points is too small to start from?
Unfortunately not, as Yambo needs regular grids so explicit calculations along a path are prohibitive.If the interpolation remains problematic: is there also a way to evaluate the QP corrections along the band structure path explicitly?
Another way to perform interpolations (also considering GW energies) that should be more accurate is to go through Wannier90 interpolation.
Here you can find an example of how to interface Wannier90 and Yambo:
https://github.com/wannier-developers/w ... /example23
https://github.com/wannier-developers/w ... c/tutorial
Best,
Daniele
Dr. Daniele Varsano
S3-CNR Institute of Nanoscience and MaX Center, Italy
MaX - Materials design at the Exascale
http://www.nano.cnr.it
http://www.max-centre.eu/
S3-CNR Institute of Nanoscience and MaX Center, Italy
MaX - Materials design at the Exascale
http://www.nano.cnr.it
http://www.max-centre.eu/
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- Posts: 4
- Joined: Sat Nov 19, 2016 5:15 pm
Re: Explicit band structure vs interpolation
Dear Daniele,
thanks for the quick reply. Indeed, using more kpoints seems to improve the interpolation. Thanks also for the heads up regarding the Wannier Interpolation, will check it out.
I still have one question regarding the ypp input. I thought would make 30 steps in each segment of the kpath. However, when I use this with:
I end up with fewer points
Am I interpreting the option wrong?
Cheers,
Bjoern
thanks for the quick reply. Indeed, using more kpoints seems to improve the interpolation. Thanks also for the heads up regarding the Wannier Interpolation, will check it out.
I still have one question regarding the ypp input. I thought
Code: Select all
BANDS_steps= 30 # Number of divisions
Code: Select all
%BANDS_kpts # K points of the bands circuit
0.0 | 0.0 | 0.5|
0.0 | 0.0 | 0.0|
Code: Select all
# |k| (a.u.) b100 b101 b102 b103 b104 b105 b106 b107 b108 b109 k_x (rlu) k_y (rlu) k_z (rlu)
#
0.00000000 -1.14401233 -0.628518105 -0.438549034E-1 0.721207082 1.30482411 2.10452604 2.34852815 2.47630310 2.91414833 2.98115277 0.00000000 0.00000000 0.500000000
0.979050528E-2 -1.14392805 -0.628578305 -0.437178910E-1 0.721195817 1.30492163 2.10455275 2.34873843 2.47617722 2.91426229 2.98114419 0.00000000 0.00000000 0.428571433
0.195810106E-1 -1.14374435 -0.628702343 -0.433938354E-1 0.721208334 1.30514252 2.10464907 2.34920573 2.47595191 2.91452813 2.98106289 0.00000000 0.00000000 0.357142895
0.293715205E-1 -1.14358652 -0.628789306 -0.430470817E-1 0.721319377 1.30535519 2.10483456 2.34963083 2.47589064 2.91480446 2.98082757 0.00000000 0.00000000 0.285714298
0.391620249E-1 -1.14352655 -0.628784657 -0.427870080E-1 0.721551120 1.30547845 2.10509872 2.34983492 2.47611928 2.91499925 2.98043609 0.00000000 0.00000000 0.214285702
0.489525311E-1 -1.14357328 -0.628688574 -0.426532105E-1 0.721867859 1.30549359 2.10540056 2.34978604 2.47660327 2.91508222 2.97996402 0.00000000 0.00000000 0.142857149
0.587430410E-1 -1.14367497 -0.628557324 -0.426261649E-1 0.722167313 1.30543911 2.10565948 2.34959292 2.47713757 2.91507792 2.97955251 0.00000000 0.00000000 0.714285374E-1
0.685335398E-1 -1.14372849 -0.628494203 -0.426325686E-1 0.722294509 1.30540347 2.10576463 2.34948444 2.47737813 2.91506124 2.97938418 0.00000000 0.00000000 0.00000000
Cheers,
Bjoern
Bjoern Baumeier
TU Eindhoven
TU Eindhoven
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OnlineDaniele Varsano
- Posts: 3844
- Joined: Tue Mar 17, 2009 2:23 pm
- Contact:
Re: Explicit band structure vs interpolation
Dear Bjoern,
Best,
Daniele
Me too, let us check what's the reason of that.I still have one question regarding the ypp input. I thought
BANDS_steps= 30 # Number of divisions
would make 30 steps in each segment of the kpath.
Best,
Daniele
Dr. Daniele Varsano
S3-CNR Institute of Nanoscience and MaX Center, Italy
MaX - Materials design at the Exascale
http://www.nano.cnr.it
http://www.max-centre.eu/
S3-CNR Institute of Nanoscience and MaX Center, Italy
MaX - Materials design at the Exascale
http://www.nano.cnr.it
http://www.max-centre.eu/