Yambo Community Forum

Dear all,

I saw that in a couple of recent papers,

https://journals.aps.org/prb/abstract/1 ... .99.081109
https://journals.aps.org/prl/abstract/1 ... 122.187401

Yambo was used to calculated luminescence.

Is this feature available in the GLP?
Is there any tutorial?

with best regards
Javad

Dear Javad,
there is not yet an automatic tool to calculate PL, hopefully, there will be soon with some documentation/tutorial.
You can anyway follow the receipt used in the papers you mention, calculate the needed quantities with Yambo and some phonon code (e.g. ph.x in QE) and calculate the PL
as a post processing.

Best,
Daniele

Dear Javad

as Daniele pointed out, there are not tutorial or automatic way to do it.
However I will explain you the different steps we have done for this kind of calculations:

1) calculate the band structure of your materials

2) find the indirect band gap, and the corresponding q-point that connect top valence and bottom conduction

3) approximate that q-point with a symmetric one, for example if you have something line 0.33222, 0.3111, 0
you can approximate it with 1/3,1/3,0

4) calculate phonons, and then using matdyn.x calculate the phonon modes corresponding to the q point of the indirect band gap

5) then you have to generate the supercell corresponding that q-point and displace atoms along the different phonon modes
(we will release soon a code to do this part)

6) recalculate the BSE in the supercell with displaced atoms, to calculate the derivatives of the excitonic dipoles.
Dipoles can be plotted with ypp -e s command.

Use the derivatives of the dipoles, exciton and phonon energies to reconstruct the formula in
https://journals.aps.org/prl/abstract/1 ... 122.187401

notice that you have to provide also the lattice temperature and the exciton temperature.

best
Claudio

ps the formula of https://journals.aps.org/prb/abstract/1 ... .99.081109
is more complicated because it requires a rotation of the electronic occupations

Dear Javad

a new tutorial is available on wiki, on phonon-assisted luminescence by finite atomic displacements.

Calculations are performed using Yambo plus YamboPy and QuantumEspresso for the phonon modes.

http://www.yambo-code.org/wiki/index.ph ... placements

best regards
Claudio Attaccalite

Dear Claudio,
I read the tutorial (Phonon-assisted luminescence by finite atomic displacements) and did the calculations, but the exciton weights on band structure plotted by exc_kspace_plot.py was wrong.
I guess I didn't think about the hint: "N. B. : in order to not recalculate W for each atomic displacement you can perform calculations without symmetries in the pristine supercell and then copy the corresponding dielectric constant in the calculations with displaced atoms".
So how can I not calculate the W for each atomic displacement?

best regards
xlWang

Dear xlWang

I added some input files to reproduce the calculations.
http://www.yambo-code.org/wiki/index.ph ... s_for_h-BN

Notice that results may depend from the parameters used in the BSE etc...
please have a look at the input and let me know.
Regarding the calculations without symmetries, when you have performed a calculation in the undistorted supercells you have to copy the SAVE/ndb.em1s* files in the displaced supercells SAVE folder in order to not recalculate W.

Best
Claudio

Dear Claudio,

Thanks for your reply.
Before calculating the BSE, the screening was calculated. The parameters are pasted below.

Screening parameters:
screen # [R] Inverse Dielectric Matrix
em1s # [R][Xs] Statically Screened Interaction
dipoles # [R] Oscillator strenghts (or dipoles)
Chimod= "HARTREE" # [X] IP/Hartree/ALDA/LRC/PF/BSfxc
% BndsRnXs
1 | 240 | # [Xs] Polarization function bands
%
NGsBlkXs= 6 Ry # [Xs] Response block size
% LongDrXs
1.000000 | 1.000000 | 1.000000 | # [Xs] [cc] Electric Field
%
XTermKind= "none" # [X] X terminator ("none","BG" Bruneval-Gonze)
-----------------------------------------------------------------------------------------------------
-----------------------------------------------------------------------------------------------------
BSE parameters:
optics # [R] Linear Response optical properties
bss # [R] BSE solver
bse # [R][BSE] Bethe Salpeter Equation.
dipoles # [R] Oscillator strenghts (or dipoles)
BSEmod= "resonant" # [BSE] resonant/retarded/coupling
BSKmod= "SEX" # [BSE] IP/Hartree/HF/ALDA/SEX/BSfxc
BSSmod= "d" # [BSS] (h)aydock/(d)iagonalization/(s)lepc/(i)nversion/(t)ddft`
BSENGexx= 30 Ry # [BSK] Exchange components
BSENGBlk= 4 Ry # [BSK] Screened interaction block size [if -1 uses all the G-vectors of W(q,G,Gp)]
#WehCpl # [BSK] eh interaction included also in coupling
KfnQPdb= "none" # [EXTQP BSK BSS] Database action
KfnQP_INTERP_NN= 1 # [EXTQP BSK BSS] Interpolation neighbours (NN mode)
KfnQP_INTERP_shells= 20.00000 # [EXTQP BSK BSS] Interpolation shells (BOLTZ mode)
KfnQP_DbGd_INTERP_mode= "NN" # [EXTQP BSK BSS] Interpolation DbGd mode
% KfnQP_E
1.440000 | 1.000000 | 1.000000 | # [EXTQP BSK BSS] E parameters (c/v) eV|adim|adim
%
KfnQP_Z= ( 1.000000 , 0.000000 ) # [EXTQP BSK BSS] Z factor (c/v)
KfnQP_Wv_E= 0.000000 eV # [EXTQP BSK BSS] W Energy reference (valence)
% KfnQP_Wv
0.000000 | 0.000000 | 0.000000 | # [EXTQP BSK BSS] W parameters (valence) eV| 1|eV^-1
%
KfnQP_Wv_dos= 0.000000 eV # [EXTQP BSK BSS] W dos pre-factor (valence)
KfnQP_Wc_E= 0.000000 eV # [EXTQP BSK BSS] W Energy reference (conduction)
% KfnQP_Wc
0.000000 | 0.000000 | 0.000000 | # [EXTQP BSK BSS] W parameters (conduction) eV| 1 |eV^-1
%
KfnQP_Wc_dos= 0.000000 eV # [EXTQP BSK BSS] W dos pre-factor (conduction)
BSEprop= "abs" # [BSS] abs/kerr/magn/dichr trace
% BSEQptR
1 | 1 | # [BSK] Transferred momenta range
%
% BSEBands
42 | 55 | # [BSK] Bands range
%
%
% BEnRange
2.00000 | 8.00000 | eV # [BSS] Energy range
%
% BDmRange
0.100000 | 0.100000 | eV # [BSS] Damping range
%
BEnSteps= 800 # [BSS] Energy steps
% BLongDir
1.000000 | 1.000000 | 0.000000 | # [BSS] [cc] Electric Field
%
WRbsWF # [BSS] Write to disk excitonic the WFs