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The problems of Bethe-Salpeter at finite temperature
Posted: Fri Apr 30, 2021 12:35 pm
by shan dong
Dear all,
I have solved the BSE at finite temperature with Yambo and referred to the following silicon example:
http://www.yambo-code.org/wiki/index.ph ... emperature I Noticed that it changed the BSE type to "coupling" in this tutorial and many exciton with negative energy after typed "ypp_ph -e s". But when I change BSEmod to" retarded", the exciton energy becomes positive, which is what I want. Does BSEmod have to be set as coupling after considering Electron Phonon Coupling? Is "KfnQP_E" the GW difference between considering and not considering Electron Phonon Coupling?
Re: The problems of Bethe-Salpeter at finite temperature
Posted: Fri Apr 30, 2021 12:43 pm
by Daniele Varsano
Dear Shan Dong,
when adding the coupling you have both resonant and antiresonant part of the matrix and this what negative energies applies in the spectrum. When discarding the coupling (Tamm-Dancoff) only the resonant part is solved as the antiresonant spectrum is exactly the negative of the resonant one.
Here you need to use the coupling as stated:
"Notice that we changed the BSE type to "coupling" because you need the full Bethe-Salpeter to deal with complex quasi-particles."
In general, KfnQP_E should be the energy correction to mimic the GW correction.
Best,
Daniele
Re: The problems of Bethe-Salpeter at finite temperature
Posted: Fri Apr 30, 2021 2:55 pm
by claudio
Dear Shan Dong
there is the possiblity to use resonant BSE at finite temperture, by means of the inversion solver.
I just updated the tutorial:
http://www.yambo-code.org/wiki/index.ph ... emperature
best
Claudio
Re: The problems of Bethe-Salpeter at finite temperature
Posted: Tue May 04, 2021 12:48 pm
by shan dong
Dear Claudio，
Thanks for your patience, I use the yambo 5.0.2, i have used resonant BSE by typing" yambo_ph -X s -o b -k sex -y i -V qp" but when i typed " ypp_ph -e s" to get the exciton energy
Code: Select all
<---> [01] MPI/OPENMP structure, Files & I/O Directories
<---> [02] Y(ambo) P(ost)/(re) P(rocessor)
<---> [03] Core DB
<---> :: Electrons : 8.000000
<---> :: Temperature : 0.000000 [eV]
<---> :: Lattice factors : 5.132000 5.132000 5.132000 [a.u.]
<---> :: K points : 8
<---> :: Bands : 12
<---> :: Symmetries : 48
<---> :: RL vectors : 9257
<---> [04] K-point grid
<---> :: Q-points (IBZ): 1
<---> :: X K-points (IBZ): 8
<---> [05] CORE Variables Setup
<---> [05.01] Unit cells
<---> [05.02] Symmetries
<---> [05.03] Reciprocal space
<---> [05.04] K-grid lattice
<---> Grid dimensions : 4 4 4
<---> [05.05] Energies & Occupations
<---> [06] Excitonic Properties @ Q-index #1
[ERROR] STOP signal received while in[06] Excitonic Properties @ Q-index #1
[ERROR] ndb.BS_diago not found
If i changed the BSEmod variable to retarded and changed the BSSmod variable to d , Things seem to ok. In the tutorial you mentioned above,"we also introduce an additional rigid shift of 0.8 eV to mimic the GW correction with the line 0.500000 | 1.000000 | 1.000000 | \# [EXTQP BSK BSS] E parameters (c/v) eV|adim|adim." I wonder why the value of KfnQP_E is 0.5 instead of 0.8.
Re: The problems of Bethe-Salpeter at finite temperature
Posted: Tue May 04, 2021 10:43 pm
by claudio
Dear Shan Dong
thank you for find the typos in the tutorial it was 0.5 in both the input and the explanation I corrected it.
Regarding the inversion solver, as specified in the tutorial (now in a better way), if you use the inversion solver
you cannot analyse the excitons you just get the spectra
best
Claudio