Dear Samaneh,
I have already answered you in a previous post.
Calculate the dynamical dielectric function at the level of theory you desire (RPA, TDDFT, HF, BSE), and look at the zero energy value.
Daniele
exciton binding energy
Moderators: Davide Sangalli, andrea marini, Daniele Varsano
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OnlineDaniele Varsano
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Re: exciton binding energy
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: 165
- Joined: Tue Jan 21, 2014 9:03 am
Re: exciton binding energy
Dear Daniele,
Yes I found it.
Thanks
Yes I found it.
Thanks
S. Ataei, PhD student at University of Tehran, Iran.
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- Posts: 31
- Joined: Wed Jan 17, 2024 12:13 pm
- Location: France
Re: exciton binding energy
Dear Daniele,
I computed the optical absorption for a 1D system. However, the energy of the peaks on my plot of the optical absorption is wrong. ( plot "o-ev_GW_3.alpha_q1_diago_bse_TEST" u 1:2 w l)
when i plot with (plot "o-ev_GW_3.alpha_q1_diago_bse_TEST" u 1:4) it seems correct.
I attached the report and output files. (Since we can add three attachments, I write the excitonic energies here.)
# Maximum Residual Value = 0.38730E+01
#
# E [ev] Strength Index
#
-0.124014705 0.999999940 1.00000000
0.15619701 0.33847322E-09 2.0000000
0.258908361 0.122013018E-1 3.00000000
0.47375387 0.92644096E-11 4.0000000
0.502913177 0.894569885E-2 5.00000000
0.74984646 0.16381771E-11 6.0000000
0.778735518 0.653948821E-2 7.00000000
0.81744349 0.54038078E-12 8.0000000
1.0005046 0.85885682E-11 9.0000000
1.02878881 0.522387633E-2 10.0000000
1.1728863 0.41521029E-12 11.000000
1.1996268 0.93699465E-10 12.000000
1.2272360 0.25179446E-12 13.000000
1.2286303 0.96458583E-12 14.000000
1.25555646 0.440468034E-2 15.0000000
1.2989506 0.13916714E-11 16.000000
1.3741199 0.52030075E-10 17.000000
1.4155179 0.37175178E-12 18.000000
1.4333268 0.28858803E-10 19.000000
1.4381497 0.11025027E-10 20.000000
1.46215904 0.393986190E-2 21.0000000
1.4740620 0.11227375E-11 22.000000
1.5333049 0.88010932E-10 23.000000
1.6097236 0.26518143E-11 24.000000
1.6208855 0.90077832E-11 25.000000
1.6253181 0.28864687E-10 26.000000
1.65039110 0.400217436E-2 27.0000000
1.6764745 0.59737519E-11 28.000000
1.7230855 0.52400878E-09 29.000000
1.7903579 0.21673523E-09 30.000000
1.8104832 0.97735570E-10 31.000000
Best,
Reza
I computed the optical absorption for a 1D system. However, the energy of the peaks on my plot of the optical absorption is wrong. ( plot "o-ev_GW_3.alpha_q1_diago_bse_TEST" u 1:2 w l)
when i plot with (plot "o-ev_GW_3.alpha_q1_diago_bse_TEST" u 1:4) it seems correct.
I attached the report and output files. (Since we can add three attachments, I write the excitonic energies here.)
# Maximum Residual Value = 0.38730E+01
#
# E [ev] Strength Index
#
-0.124014705 0.999999940 1.00000000
0.15619701 0.33847322E-09 2.0000000
0.258908361 0.122013018E-1 3.00000000
0.47375387 0.92644096E-11 4.0000000
0.502913177 0.894569885E-2 5.00000000
0.74984646 0.16381771E-11 6.0000000
0.778735518 0.653948821E-2 7.00000000
0.81744349 0.54038078E-12 8.0000000
1.0005046 0.85885682E-11 9.0000000
1.02878881 0.522387633E-2 10.0000000
1.1728863 0.41521029E-12 11.000000
1.1996268 0.93699465E-10 12.000000
1.2272360 0.25179446E-12 13.000000
1.2286303 0.96458583E-12 14.000000
1.25555646 0.440468034E-2 15.0000000
1.2989506 0.13916714E-11 16.000000
1.3741199 0.52030075E-10 17.000000
1.4155179 0.37175178E-12 18.000000
1.4333268 0.28858803E-10 19.000000
1.4381497 0.11025027E-10 20.000000
1.46215904 0.393986190E-2 21.0000000
1.4740620 0.11227375E-11 22.000000
1.5333049 0.88010932E-10 23.000000
1.6097236 0.26518143E-11 24.000000
1.6208855 0.90077832E-11 25.000000
1.6253181 0.28864687E-10 26.000000
1.65039110 0.400217436E-2 27.0000000
1.6764745 0.59737519E-11 28.000000
1.7230855 0.52400878E-09 29.000000
1.7903579 0.21673523E-09 30.000000
1.8104832 0.97735570E-10 31.000000
Best,
Reza
You do not have the required permissions to view the files attached to this post.
Reza - Postdoc
CNRS
CNRS
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OnlineDaniele Varsano
- Posts: 3842
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Re: exciton binding energy
Dear Reza,
what do you mean by "wrong" and "right"?
The fourth column is the independent particle spectrum, with excitations corresponding to Ec-Ev and the onset in the position of the gap.
In the second column you have the result of the BSE and you get a binding energy larger than the gap, resulting in a negative excitation (instability), the spectrum is negative for positive energy because of the time-ordering. It is up to you to check if it is physical or not. I suggest you to check the convergence parameter both in GW and in BSE, in particular the k point sampling.
Best,
Daniele
what do you mean by "wrong" and "right"?
The fourth column is the independent particle spectrum, with excitations corresponding to Ec-Ev and the onset in the position of the gap.
In the second column you have the result of the BSE and you get a binding energy larger than the gap, resulting in a negative excitation (instability), the spectrum is negative for positive energy because of the time-ordering. It is up to you to check if it is physical or not. I suggest you to check the convergence parameter both in GW and in BSE, in particular the k point sampling.
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/
-
- Posts: 31
- Joined: Wed Jan 17, 2024 12:13 pm
- Location: France
Re: exciton binding energy
Dear Daniele,
I did my calculation using larger k-points. However, the optical absorption shape is strange and not compatible with the exciton energy range. I attached the needed files for analysis.
When I increase the k points from 50 to 70, the size of the band gap is similar in both cases.
Best,
Reza
I did my calculation using larger k-points. However, the optical absorption shape is strange and not compatible with the exciton energy range. I attached the needed files for analysis.
When I increase the k points from 50 to 70, the size of the band gap is similar in both cases.
Best,
Reza
You do not have the required permissions to view the files attached to this post.
Reza - Postdoc
CNRS
CNRS
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OnlineDaniele Varsano
- Posts: 3842
- Joined: Tue Mar 17, 2009 2:23 pm
- Contact:
Re: exciton binding energy
Dear Reza,
the shape is due to the fact you have a negative excitation energy which hinder an instability of your system. You should carefully check your convergence both at GW and BSE level.
Anyway, I noticed in your report you have used database coming from different calculations (a different SAVE directory) and this is dangerous and error-prone. See the many warning in your report:
I strongly discourage to do this.
Next, you are using the WS cutoff, this should work, but it is not extensively tested, you can try to use a different cutoff as the "box x" together with the rim_cut to check in case this is giving some problem.
Other parameters to check are:
BndsRnXp: considering you have 66 occupied bands, 100 bands seem to be rather low
BSENGexx: this can be converged, but can be veirified, increasing its value does not cost much.
Best,
Daniele
the shape is due to the fact you have a negative excitation energy which hinder an instability of your system. You should carefully check your convergence both at GW and BSE level.
Anyway, I noticed in your report you have used database coming from different calculations (a different SAVE directory) and this is dangerous and error-prone. See the many warning in your report:
Code: Select all
[WARNING] Incompatible serial number for ./job_00_first_run/
Next, you are using the WS cutoff, this should work, but it is not extensively tested, you can try to use a different cutoff as the "box x" together with the rim_cut to check in case this is giving some problem.
Other parameters to check are:
BndsRnXp: considering you have 66 occupied bands, 100 bands seem to be rather low
BSENGexx: this can be converged, but can be veirified, increasing its value does not cost much.
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/