yambo calculate the exciton lifetime
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 Posts: 22
 Joined: Fri Mar 26, 2021 11:27 am
yambo calculate the exciton lifetime
Dear friends:
I am a novice who use yambo to calculate the character of exciton,recently ,i have a question about calculating the lifetime of exciton.
The formulate calculate the lifetime in an article:Ab initio calculations of exciton radiative lifetimes in bulk crystals, nanostructures, and molecules.
In that article,i know that Rs2D(0) as the recombination rate for Q=0,Rs2D(0)=((e^2)*(Ps^2))/[(8.854187817 × 1012)*(m^2)*c*A*Es(0)].
the m is the quality of electron,the permittivity of vacuum is t0=8.854187817 × 1012,c is the spead of light，A is the area of the system in the xy plane,e is the electron charge,Es(0) is the exciton energy,Ps is the exciton transition dipole. So I want to know how to calculate the Ps by using yambo.
In addition,i have read another article:Exciton Radiative Lifetimes in TwoDimensional Transition Metal Dichalcogenides.the recombination rate for Q =0,could be expressed as :(8*Π*(e^2)*Es(0)*Us^2)/((h/2Π）*c*A),Us^2 is the square modulus of the BSE exciton transition dipole divided by the number of unit cells in 2D in the system.(i.e., the number of 2D kpoints employed in the calculation),so how to calculate the Us^2?
what is the relation between exciton transition dipole and the strenth in the document which called ~.exc_E_sorted？
Thanks for your read，please help me to understand that.
I hope you are well and in good health!
Best wishes!
Quxiao
I am a novice who use yambo to calculate the character of exciton,recently ,i have a question about calculating the lifetime of exciton.
The formulate calculate the lifetime in an article:Ab initio calculations of exciton radiative lifetimes in bulk crystals, nanostructures, and molecules.
In that article,i know that Rs2D(0) as the recombination rate for Q=0,Rs2D(0)=((e^2)*(Ps^2))/[(8.854187817 × 1012)*(m^2)*c*A*Es(0)].
the m is the quality of electron,the permittivity of vacuum is t0=8.854187817 × 1012,c is the spead of light，A is the area of the system in the xy plane,e is the electron charge,Es(0) is the exciton energy,Ps is the exciton transition dipole. So I want to know how to calculate the Ps by using yambo.
In addition,i have read another article:Exciton Radiative Lifetimes in TwoDimensional Transition Metal Dichalcogenides.the recombination rate for Q =0,could be expressed as :(8*Π*(e^2)*Es(0)*Us^2)/((h/2Π）*c*A),Us^2 is the square modulus of the BSE exciton transition dipole divided by the number of unit cells in 2D in the system.(i.e., the number of 2D kpoints employed in the calculation),so how to calculate the Us^2?
what is the relation between exciton transition dipole and the strenth in the document which called ~.exc_E_sorted？
Thanks for your read，please help me to understand that.
I hope you are well and in good health!
Best wishes!
Quxiao
Quxiao in BIT,calculate the exciton

 Posts: 14
 Joined: Wed Apr 01, 2009 8:10 am
 Location: Dipartimento di Fisica Universita' Tor Vergata Roma
 Contact:
Re: yambo calculate the exciton lifetime
Dear Qxiao
the two formulas are the same beyond a factor 2 due to a wrong normalization to sqrt(2) instead of 1 in the first derivation.
see the discussion at pag 3842 before eq. 11 of this paper H.Chen et al Nano Letters https://doi.org/10.1021/acs.nanolett.8b01114
In the first paper we used CGS in the second and in Phys. Rev. B 100, 075135 we used MKS
The factor A is the area of the unit cell multiplied by the number of kpoints used in the BSE simulation.
Yes in principle you can use the o*sorted file but pay attention because in that file the oscillator strength (= the modulus square of the excitonic dipole)
is normalized to the maximum value but you can find this maximum value at the beginning of the file.
Best
Maurizia
the two formulas are the same beyond a factor 2 due to a wrong normalization to sqrt(2) instead of 1 in the first derivation.
see the discussion at pag 3842 before eq. 11 of this paper H.Chen et al Nano Letters https://doi.org/10.1021/acs.nanolett.8b01114
In the first paper we used CGS in the second and in Phys. Rev. B 100, 075135 we used MKS
The factor A is the area of the unit cell multiplied by the number of kpoints used in the BSE simulation.
Yes in principle you can use the o*sorted file but pay attention because in that file the oscillator strength (= the modulus square of the excitonic dipole)
is normalized to the maximum value but you can find this maximum value at the beginning of the file.
Best
Maurizia
Dipartimento di Fisica
Universita' 'Tor Vergata'
Via della Ricerca Scientifica I
tel.++390672594894
fax.++39062023507
http://www.fisica.uniroma2.it/~cmtheogroup/
ETSF European Theoretical Spectroscopy Facility www.etsf.eu
Universita' 'Tor Vergata'
Via della Ricerca Scientifica I
tel.++390672594894
fax.++39062023507
http://www.fisica.uniroma2.it/~cmtheogroup/
ETSF European Theoretical Spectroscopy Facility www.etsf.eu

 Posts: 22
 Joined: Fri Mar 26, 2021 11:27 am
Re: yambo calculate the exciton lifetime
Dear Palummo Maurizia:
Thank you so much for your reply!
However,I still have some questions。
Fistly，I want to ensure that if the Us^2 of the formular is the oscillator strength？My understanding about your reply is that the Us^2 is equal to the oscillator,right？
Secondly,I read your reply :"the oscillator strength is normalized to the maximum value",so I use the maximum value multiply the strength.
Then, as you said, "in principle you can use the o*sorted file",so you don not use that method,maybe you have another file to get that Us^2?or I understand that mistakely?
The last question:I make calculation of the MoS2,the oder of magnitude is not correct,so I suppose that if the unit of the strength were not the MSK?maybe that need some transition about the unit?
Sincere thanks for your help and guidance!
Best wishes!
Qu Xiao
BIT
Thank you so much for your reply!
However,I still have some questions。
Fistly，I want to ensure that if the Us^2 of the formular is the oscillator strength？My understanding about your reply is that the Us^2 is equal to the oscillator,right？
Secondly,I read your reply :"the oscillator strength is normalized to the maximum value",so I use the maximum value multiply the strength.
Then, as you said, "in principle you can use the o*sorted file",so you don not use that method,maybe you have another file to get that Us^2?or I understand that mistakely?
The last question:I make calculation of the MoS2,the oder of magnitude is not correct,so I suppose that if the unit of the strength were not the MSK?maybe that need some transition about the unit?
Sincere thanks for your help and guidance!
Best wishes!
Qu Xiao
BIT
Quxiao in BIT,calculate the exciton

 Posts: 14
 Joined: Wed Apr 01, 2009 8:10 am
 Location: Dipartimento di Fisica Universita' Tor Vergata Roma
 Contact:
Re: yambo calculate the exciton lifetime
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
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
Dipartimento di Fisica
Universita' 'Tor Vergata'
Via della Ricerca Scientifica I
tel.++390672594894
fax.++39062023507
http://www.fisica.uniroma2.it/~cmtheogroup/
ETSF European Theoretical Spectroscopy Facility www.etsf.eu
Universita' 'Tor Vergata'
Via della Ricerca Scientifica I
tel.++390672594894
fax.++39062023507
http://www.fisica.uniroma2.it/~cmtheogroup/
ETSF European Theoretical Spectroscopy Facility www.etsf.eu
 Daniele Varsano
 Posts: 2997
 Joined: Tue Mar 17, 2009 2:23 pm
 Contact:
Re: yambo calculate the exciton lifetime
Dear Qxiao,
the dipole units in yambo are in bohr!
Best,
Daniele
the dipole units in yambo are in bohr!
Best,
Daniele
Dr. Daniele Varsano
S3CNR Institute of Nanoscience and MaX Center, Italy
MaX  Materials design at the Exascale
http://www.nano.cnr.it
http://www.maxcentre.eu/
S3CNR Institute of Nanoscience and MaX Center, Italy
MaX  Materials design at the Exascale
http://www.nano.cnr.it
http://www.maxcentre.eu/

 Posts: 22
 Joined: Fri Mar 26, 2021 11:27 am
Re: yambo calculate the exciton lifetime
Dear Palummo Maurizia:
I am so exciting to get your reply,it is so useful that solve my puzzle！
Thank you for all your assistance！
Best wishes！
Quxiao
I am so exciting to get your reply,it is so useful that solve my puzzle！
Thank you for all your assistance！
Best wishes！
Quxiao
Quxiao in BIT,calculate the exciton

 Posts: 22
 Joined: Fri Mar 26, 2021 11:27 am
Re: yambo calculate the exciton lifetime
Dear Daniele Varsano:
Firstly,thanks for your help!I learn that "the dipole units in yambo are in bohr!'from your reply,it is important for me to ensure that ,the units of the oscillator strength is the squre of bohr(bohr^2),is it?
Finally，thanks for your help again！And thanks for the guidance from Prof.Palummo Maurizia ！
Best wishes
Quxiao
Firstly,thanks for your help!I learn that "the dipole units in yambo are in bohr!'from your reply,it is important for me to ensure that ,the units of the oscillator strength is the squre of bohr(bohr^2),is it?
Finally，thanks for your help again！And thanks for the guidance from Prof.Palummo Maurizia ！
Best wishes
Quxiao
Quxiao in BIT,calculate the exciton
 Daniele Varsano
 Posts: 2997
 Joined: Tue Mar 17, 2009 2:23 pm
 Contact:
Re: yambo calculate the exciton lifetime
Dear Quxiao,
the strengths reported in the o*sorted file should have the unit of energy. And if I'm not wrong is already in eV.
You can have a look to this thread.
Best,
Daniele
the strengths reported in the o*sorted file should have the unit of energy. And if I'm not wrong is already in eV.
You can have a look to this thread.
Best,
Daniele
Dr. Daniele Varsano
S3CNR Institute of Nanoscience and MaX Center, Italy
MaX  Materials design at the Exascale
http://www.nano.cnr.it
http://www.maxcentre.eu/
S3CNR Institute of Nanoscience and MaX Center, Italy
MaX  Materials design at the Exascale
http://www.nano.cnr.it
http://www.maxcentre.eu/

 Posts: 22
 Joined: Fri Mar 26, 2021 11:27 am
Re: yambo calculate the exciton lifetime
Dear Daniele Varsano:
I understand that units after reading the link you shared
Thanks for your patient!
Best Wishes!
Quxiao
BIT
I understand that units after reading the link you shared
Thanks for your patient!
Best Wishes!
Quxiao
BIT
Quxiao in BIT,calculate the exciton

 Posts: 22
 Joined: Fri Mar 26, 2021 11:27 am
Re: yambo calculate the exciton lifetime
Dear Palummo MauriziaPalummo Maurizia wrote: ↑Sun Mar 28, 2021 5:53 pmDear Qxiao
the two formulas are the same beyond a factor 2 due to a wrong normalization to sqrt(2) instead of 1 in the first derivation.
see the discussion at pag 3842 before eq. 11 of this paper H.Chen et al Nano Letters https://doi.org/10.1021/acs.nanolett.8b01114
In the first paper we used CGS in the second and in Phys. Rev. B 100, 075135 we used MKS
The factor A is the area of the unit cell multiplied by the number of kpoints used in the BSE simulation.
Yes in principle you can use the o*sorted file but pay attention because in that file the oscillator strength (= the modulus square of the excitonic dipole)
is normalized to the maximum value but you can find this maximum value at the beginning of the file.
Best
Maurizia
I also want to ensure that，when I solve the BSE，the number of kpoints what I used would reduced due to the symmetry,so which the number I choose to multiplied? The number of kpoints in the whole brillouin zone，or in the irreducible?" The factor A is the area of the unit cell multiplied by the number of kpoints used in the BSE simulation."
Thanks so much for your help
Best wishes!
BIT Quxiao
Quxiao in BIT,calculate the exciton