lifetime calculation

[kazemoor]

Hello everyone

I am trying to calculate the quasiparticle lifetime of metals and semiconductors. In yambo one tutorial is available "real-axis GW and lifetimes". But through the example, there are ambiguous points I have faced which are my questions:

1-for Al case ,before doing any GW calculation, yambo -l give us mass-shell (z=1) lifetimes. Is it true ?
2- why some of electronic excitation lifetimes are negative. what does it mean? or is it the convention of the code which prints with negative sign?
3- For metals, near the Fermi energy, the el-ph scattering is also important. is it possible to take into account the contribution of el-ph scattering lifetime using electron-phonon tutorial section in yambo?

Thanks a lot

Ali Kazempour, Physics dept,Pnu university, Yazd, Iran

[andrea marini]

1-for Al case ,before doing any GW calculation, yambo -l give us mass-shell (z=1) lifetimes. Is it true ?

Yes. It is true.

2- why some of electronic excitation lifetimes are negative. what does it mean? or is it the convention of the code which prints with negative sign?

Yambo uses the convention that at zero temperature the imaginary part of the self-energy changes sign accross the Fermi Level and the lifetimes do the same.

3- For metals, near the Fermi energy, the el-ph scattering is also important. is it possible to take into account the contribution of el-ph scattering lifetime using electron-phonon tutorial section in yambo?

The way Yambo computs e-p interaction is too complicated at the moment due to the fact that the interface with QE is out-of-date. We are working on this and in the new release of Yambo the e-p interaction should be fully working.

Andrea

[Khaled]

Dear developers,

I am trying to calculate lifetimes by typing yambo -l, always I get empty input file. I attached required files.

I am looking for your valuable suggestion. Thank you in advance.

Best regards,
khaled.

[Daniele Varsano]

Dear Khaled,
can you please more specific on what step you did?
You posted report files of a GW plasmon-pole calculations, so it looks that the code is installed and working properly.
Are you receiving any message?
Best,
Daniele

[Khaled]

Dear Dr. Daniele,

I did the following
1) For GW calculation I created the input file by using this command "yambo -p p -g n". then I submitted this job by using this command "yambo -F G0W0.in -J GoWo_out".

2) After the job was done I wrote "yambo -l" , I got only empty input file, I attached this file.

I do suspect that the problem in "yambo -G0W0.in -J G0W0_out" because "-J G0W0_out" putted the database file in this G0W0 which are created by GW calculation not in SAVE directory. Is that true ?. I tried to copy GW database generated during GW calculation to SAVE directory, but also didn't work.

N.B: I have read almost all lifetime calculation problem posted in this site. I appreciate your help and your effort. I'd like to provide me with the theory beyond lifetime calculation.

Thank you in advance and in your fast respond.

Best regards,

Khaled.

[Daniele Varsano]

Dear Khaled,

I do suspect that the problem in "yambo -G0W0.in -J G0W0_out" because "-J G0W0_out" putted the database file in this G0W0 which are created by GW calculation not in SAVE directory. Is that true ?. I tried to copy GW database generated during GW calculation to SAVE directory, but also didn't work.

No, in order to work you need in the SAVE directory the electronic structure database (obtained via the interfaces p2y/a2y) and the database generated by the setup. So this should not be the problem. Moreover yambo complains when does not fine needed files.
Honestly it is quite strange what you are experiencing. Try to start from scratch (setup, and lifetime input generation) and please report again, eventually we would need to reproduce your problem.
Best,
Daniele

[Khaled]

Dear Dr. Daniele,

Thank you a lot Dr. Daniele. I did but still the same problem. I am using yambo 3.4.1 rev.3187. Please let me know about that issue or any alternative ways to solve this problem.

I have some other questions, please clarify it to me one by one.
1)I need to draw exciton wave function w.r.t real space (definitely, I need wave function square ), I have already the index of the exciton I am interested in, I got it by using "yamo -e s" , then I submit the input file "yambo -e w" , the output only allow me to make visualization on xcrysden .(your discussion about using xcrysden , I have had read it).

2) For the parameter " Direction= "13" # [rlu] [1/2/3] for 1d or [12/13/23] for 2d [123] for 3d" , Are 1, 2, 3 mean lattice coordinates in different direction lets say 1 in x direction and 2 in y direction ... and 12 in x-y direction and 13 x-z ..etc. ? Is that true ?.

3) For the Parameter " Format= "g" # Output format [(c)ube/(g)nuplot/(x)crysden]". "g" only work for 1D ! why ? ,and its output two columns, can you clarify what is the first column and the second one ?
# ||a1 [A]
0.000000 0.171665


4) I did band interpolation by using ypp but my problem in drawing the band structure from o-file is generated by ypp which it includes
kx ky kz b40 b41
0.0000000000 0.0000000000 0.0000000000 -0.3440745473 4.84708690

How can I draw Band structure by using these 5 columns. pleas advice me ?.

Thank you in advance and I am waiting for available suggestions. I appreciate your help Dr. Daniele,

Best regards,
Khaled.

[Daniele Varsano]

Dear Khaled,

Please let me know about that issue or any alternative ways to solve this problem.

We will have a look, in the meanwhile you can either try to switch to the new version of the code (4.x) or copy a lifetime template input from the tutorial, modify it according to your needs, and try to run it.

1)I need to draw exciton wave function w.r.t real space (definitely, I need wave function square ), I have already the index of the exciton I am interested in, I got it by using "yamo -e s" , then I submit the input file "yambo -e w" , the output only allow me to make visualization on xcrysden .(your discussion about using xcrysden , I have had read it).

In the ypp input file you can choose among different format:

Code: Select all

Format= "c/g/x"                  # Output format [(c)ube/(g)nuplot/(x)crysden]

you can use gnuplot for 1d plot, gnuplot and xcrysden for 2D and cube/xcrysden for 3D.
Anyway what's your problem in using xcrysden?

2) For the parameter " Direction= "13" # [rlu] [1/2/3] for 1d or [12/13/23] for 2d [123] for 3d" , Are 1, 2, 3 mean lattice coordinates in different direction lets say 1 in x direction and 2 in y direction ... and 12 in x-y direction and 13 x-z ..etc. ? Is that true ?.

Yes , the wfs is integrated (averaged) in the direction not considered in the plot.

3) For the Parameter " Format= "g" # Output format [(c)ube/(g)nuplot/(x)crysden]". "g" only work for 1D ! why ? ,and its output two columns, can you clarify what is the first column and the second one ?
# ||a1 [A]
0.000000 0.171665

Well, I was thinking it should work also for 2D, anyway I have to check it in the current version of the code. 3D is not supported as gnuplot actually does not include the possibility to do isosurface plots. The meaning is:
Column 1: position along the choosen direction s
Column2: wfs(s), where it has been averaged over the other two spatial coordinates.

4) I did band interpolation by using ypp but my problem in drawing the band structure from o-file is generated by ypp which it includes
kx ky kz b40 b41
0.0000000000 0.0000000000 0.0000000000 -0.3440745473 4.84708690
How can I draw Band structure by using these 5 columns. pleas advice me ?.

By using gnuplot you can plot them using the command:

Code: Select all

plot "o-file" u 0:4,  "o-file" u 0:5 

in abscissa you will have increasing integers, that you can rename according the path you have choosen to plot the band structure, which correspond to the k point vectors with the components indicated in the first 3 columns.


Best,
Daniele

[Khaled]

Dear Dr Daniele Varsano,

I appreciate your great job and your effort. Thank you a lot. "ypp -e w " is working well with me, I selected the exciton which it has high intensity and this exciton has energy larger than energy of the band gap but exciton works below the band gap energy, Presently I am working with the exciton below the band gap and the calculation went well. I have some question just for clarification reasons, please answer me one by one.

1) the second output file which is created by "ypp -e a" as the following
Band_V Band_C K ibz Symm. Weight Energy
#
40.00000 42.00000 6.00000 3.00000 0.12496 1.94498
a) Are Band_V and Band_C in which e-h pairs exist ? but in my structure max.V_band is 40 and min_C_band is 41, what I found looks strange for me, see attachment.

b) I don't understand what " Symm " in this file mean physically here ? !

2)I have question for "ypp -e w", there is input value in exciton input file
% Hole
# | 0.662611 | 0.000000 | 0.596785 | # [cc] Hole position in unit cell
I tried to change the hole position by putting the positions of different atoms in my structure but when the calculation done and I see the positions in outputs file I found yambo changed these positions with totally different values, I did it many times for different position and I got different thing. why? I don't understand this behaviours (N.B : these positions are coming from atomic positions card in my DFT files).

3) For the Band interpolation. If I let GfnQpdb ="none" this means, I do Band interpolation for DFT calculation ?.

4)Finally, Regarding to the Lifetime calculations, I did what u said last time ? but the problem still exist.


Best regards,

Khaled.

[Daniele Varsano]

Dear Khaled,

but exciton works below the band gap energy

Well no, excitons can be bound or not.

a) Are Band_V and Band_C in which e-h pairs exist ? but in my structure max.V_band is 40 and min_C_band is 41, what I found looks strange for me, see attachment.

Yes, electron hole pairs building up the exciton. I can't see nothing strange here, what you mean by "strange? This is telling that the exciton is formed by these bands with a certain weight.

b) I don't understand what " Symm " in this file mean physically here ? !

Kibz it e k points in the "irreducilble" Bz, next it is expanded according to the symmetries of the system. Here it is telling you that the kpoint number 6 expanded accoring to the symmetries number 3 is contributing. The symmetries and respective indexes are written in the report files.

tried to change the hole position by putting the positions of different atoms in my structure but when the calculation done and I see the positions in outputs file I found yambo changed these positions with totally different values, I did it many times for different position and I got different thing. why? I don't understand this behaviours (N.B : these positions are coming from atomic positions card in my DFT files).

The exciton wavefunction is calcualted in a real space grid given by the FFT. The code calculate it in the point of the FFT grid which is the nearest to the position you indicated. If you repeat the number of cells then the point is then translated in the central unit cell.

3) For the Band interpolation. If I let GfnQpdb ="none" this means, I do Band interpolation for DFT calculation ?.

Yes

4)Finally, Regarding to the Lifetime calculations, I did what u said last time ? but the problem still exist.

No idea on what is happening there, as I told you I was not able to reproduce your problem, as I suggested you before you can edit your input file by hand.

Best,
Daniele