## full GW+BSE calculation

Run-time issues concerning Yambo that are not covered in the above forums.

Moderators: Daniele Varsano, andrea marini, Conor Hogan, myrta gruning

### Re: full GW+BSE calculation

Dear Khaled,

1) When you solve the BSE, the meaningful part of the exciton energy is the real part. If you are interested in exciton lifetime you need to do a model for it first.
2) If you want to extract the transition dipole matrix you can write them either looking into ./src/bse/K_diag_compute_epsilon.F, when the epsilon is built after the diagonalization of the dielectric matrix.
Otherwise with the postprocessing ypp, when excitons are sorted out (have a look in ./ypp/exciton_sort_and_report.F), the BS_R are read, normalized and printed out.

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/

Daniele Varsano

Posts: 2052
Joined: Tue Mar 17, 2009 2:23 pm

### Re: full GW+BSE calculation

Dear Dr. Daniele Varsano,

Thanks a lot Dr. Daniele for your great help. I was able to extract the transition dipole matrix, but I am not sure a bout the units of the transition dipole matrix $| \sum_{vck} \langle vq-k | e^{-iqr} | ck \rangle A_{\lambda} |^{2}$
because I extracted this term alone (even I couldn't figure out if you used the electric dipole approimation for this term or not). Please, Can you help me for getting this information. Thank you in advance.

Best regards,

Khaled.
Khaled Shehata,
PhD Student,
School of Physics,
Witwatersrand University
Khaled

Posts: 21
Joined: Fri Apr 10, 2015 10:11 am
Location: South Africa

### Re: full GW+BSE calculation

Dear Khaled,
the internal unit in the code is the atomic unit (bohr for length, Hartree for energy etc..).
The electric dipole approximation it is used for the q=0 term.

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/

Daniele Varsano

Posts: 2052
Joined: Tue Mar 17, 2009 2:23 pm

### Re: full GW+BSE calculation

What is exactly the unit of the matrix elements ?

A transition dipole has SI units of Coulomb.meters, so here, should it be electron charge.bohr ?
Thierry Clette
Student at Université Libre de Bruxelles, Belgium
Flex

Posts: 37
Joined: Fri Mar 25, 2016 4:21 pm

### Re: full GW+BSE calculation

Dear Thierry,
yes, it should be as you wrote.

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/

Daniele Varsano

Posts: 2052
Joined: Tue Mar 17, 2009 2:23 pm

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