yambo calculate the exciton lifetime

Anything regarding the post-processing utility (e.g. excitonic wavefunction analysis) is dealt with in this forum.

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Palummo Maurizia
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Re: yambo calculate the exciton lifetime

Post by Palummo Maurizia » Tue Jun 29, 2021 5:58 pm

Dear Qxiao

yes Nk is the number of k-points in the full BZ.

Best
Maurizia
Dipartimento di Fisica
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Quxiao
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Re: yambo calculate the exciton lifetime

Post by Quxiao » Thu Jul 01, 2021 5:36 am

Dear Palummo Maurizia:
Thank you very much for your help and your patience!
I think I've got it with your help
Best wishes!
Quxiao
BIT
Quxiao in BIT,calculate the exciton

Quxiao
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Re: yambo calculate the exciton lifetime

Post by Quxiao » Thu Oct 28, 2021 12:00 pm

Dear Palummo Maurizia:
Recently,I have a new question about the exciton lifetime expression,
In this paper,https://doi.org/10.1021/acs.nanolett.8b01114,according the dipole and the exciton energy,the exciton lifetime could be calculated ,which could be seen in picture 1.
The Nk is the number of the k-points,if I chose more k-points,the exciton lifetime would be changed?is it?
For example,the first ,I choose 12*12*1 as the number,the second,I choose 20*20*1 .If the results would be changed?
I do that two different calculations,find the exciton lifetime has been changed.
That paper,the support materials,Supplementary Information for:Exciton Radiative Lifetimes inLayered Transition Metal Dichalcogenides
shows that oscillator strength(picture 2),it is related to the Nk,so when the Nk tend to infinite,the oscillator tend to zero,is it?
I think the Nk should be offset,if there was someting that I have not considered?
Best Wishes!
BIT Quxiao
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Quxiao in BIT,calculate the exciton

Palummo Maurizia
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Re: yambo calculate the exciton lifetime

Post by Palummo Maurizia » Fri Oct 29, 2021 4:34 pm

Dear Qxiao

N_k is needed since you have a sum over k in the numerator. See also the formula for the macroscopic dielectric function in the
first paper of yambo https://doi.org/10.1016/j.cpc.2009.02.003 to see what I am speaking about.
In any case if you want to obtain mu_S^2 from the residuals^2 written by yambo
in the o*exc*E_sorted file do in this way:
take the second column of the file and multiply by the Maximum Residual Value you read at the beginning of the file
these are the modulus square of the residuals now not normalized to 1.
From them to obtain the modulus square of excitonic dipoles
mu_S^2 = residuals^2*Omega*N_k/(4*pi*HA2EV*n_spin)
where Omega is the volume of the cell in real space, HA2EV is the conversion from Hartree to eV and n_spin=2 for non spin-polarized case and 1 for soc, spin-polarized .

Best
Maurizia
Dipartimento di Fisica
Universita' 'Tor Vergata'
Via della Ricerca Scientifica I
tel.++39-06-72594894
fax.++39-06-2023507
http://www.fisica.uniroma2.it/~cmtheo-group/

ETSF European Theoretical Spectroscopy Facility www.etsf.eu

Quxiao
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Re: yambo calculate the exciton lifetime

Post by Quxiao » Fri Mar 24, 2023 9:06 am

Palummo Maurizia wrote: Tue Mar 30, 2021 12:56 pm Dear Qxiao

we implemented a routine in ypp in one old version of yambo that is not available anymore.
yes you can use the o*sorted* file and yes , mu_s^2. (that I imagine is your Us^2 right?) is what is written inside o*exc* file beyond the normalization.
so yes you can take those numbers and multiply them with the maximum.
The order of magnitude should be similar, so yes I suspect a problem of units.

Best
Maurizia
Dear Palummo Maurizia:
Thank you very much for your previous help!
After repeatedly repeating your multiple articles and reading the code, I have understood the relationship between all quantities. However, I still have some doubts about the unit system, but I believe I will understand. Thank you very much for your help!
Best wishes
Quxiao
Quxiao in BIT,calculate the exciton

SAM
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Re: yambo calculate the exciton lifetime

Post by SAM » Tue Jan 30, 2024 4:31 pm

Dear yambo user,
I am a new user of yambo, I am having difficulty calculating the lifespan of excitons with yambo. I don't know if it excites a yambo command to calculate the lifetime of exciteons with yambo so please help me on this. If there is a tutorial that I can go to and learn how to calculate the lifespan of exciters that would be a pleasure. I also have another concern about calculating the luminescence of the excitons the tutorials exist on the yambo site for calculating the luminescence the tarz files are not downloadable in order to be able to make an example of application if I could have the tarz files that would help me a lot.
THANKS

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Daniele Varsano
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Re: yambo calculate the exciton lifetime

Post by Daniele Varsano » Wed Jan 31, 2024 10:18 am

Dear SAM,

please sign your post with your name and affiliation. This is a rule of the forum, and you can do once for all by filling the signature in the user profile.

1. Radiative lifetime can be calculated following Palummo et al. Nano Lett. 2015, 15, 5, 2794–2800 (https://doi.org/10.1021/nl503799t).
Yambo calculate all the needed quantities, and then you need to calculate the lifetime externally. You can use yambo-py to extract what you need from the databases generated by Yambo.

2. Phonon assisted luminescence: the tutorial can be found here:
https://www.yambo-code.eu/wiki/index.ph ... placements

The broken links to the tar files now should be fixed.

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/

SAM
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Joined: Tue Jan 30, 2024 3:36 pm

Re: yambo calculate the exciton lifetime

Post by SAM » Fri Feb 09, 2024 6:35 pm

dear Daniele Varsano
Thank you for your reply.
However, I still have a concern about the calculation of the exciton lifetime. I know the theory but how to apply it to yambo is my difficulty. Once in yambo, what command should I use to calculate exciton lifetimes? If you could perhaps give me details of the commands to use, that would help me a lot.
SAM
PhD student, University of Lomé/Togo

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Daniele Varsano
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Re: yambo calculate the exciton lifetime

Post by Daniele Varsano » Mon Feb 12, 2024 9:11 am

Dear Sam,

there is not a built-in workflow for the calculation of exciton lifetimes. You need to calculate excitation energies at BSE level and then calculate the radiative lifetime externally, combining the needed quantities calculated by Yambo (see the post by Maurizia below in the same thread).

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/

nilesh12
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Re: yambo calculate the exciton lifetime

Post by nilesh12 » Wed Feb 21, 2024 9:49 pm

Dear all
I am trying to calculate the exciton radiative lifetime. I am a little bit confused about mu_s^2. I read a lot for post answers on this topic here but still, I would like to ask that
the mu_s^2 is equal to the "oscillator strength*Maximum Residual " or
I have to use this equation mu_S^2 = oscillator strength*Maximum Residual *Omega*N_k/(4*pi*HA2EV*n_spin), to calculate mu_S^2.
Please help me with this.

& please correct me if anything is wrong in this equation.

Thank you

Regards
Nilesh
Nilesh Kumar
University of Ostrava

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