BDmRange in BSE calculation

[WEI Wei]

Dear all,
I have finished a BSE calculation, attached please find the BSE spectra. The yambo.in file is as following:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
em1s # [R Xs] Static Inverse Dielectric Matrix
optics # [R OPT] Optics
bse # [R BSK] Bethe Salpeter Equation.
bss # [R BSS] Bethe Salpeter Equation solver
BSresKmod= "xc" # [BSK] Resonant Kernel mode. (`x`;`c`;`d`)
BScplKmod= "none" # [BSK] Coupling Kernel mode. (`x`;`c`;`d`;`u`)
% BSEBands
14 | 21 | # [BSK] Bands range
%
BSENGBlk= 400 RL # [BSK] Screened interaction block size
BSENGexx= 11733 RL # [BSK] Exchange components
% QpntsRXs
1 | 43 | # [Xs] Transferred momenta
%
% BndsRnXs
1 | 250 | # [Xs] Polarization function bands
%
NGsBlkXs= 400 RL # [Xs] Response block size
% LongDrXs
1.000 | 0.000 | 0.000 | # [Xs] [cc] Electric Field
%
BSSmod= "h" # [BSS] Solvers `h/d/i/t`
% BEnRange
0.00000 | 20.00000 | eV # [BSS] Energy range
%
% BDmRange
0.100000 | 0.200000 | eV # [BSS] Damping range
%
BEnSteps= 1000 # [BSS] Energy steps
% BLongDir
1.000000 | 0.000000 | 0.000000 | # [BSS] [cc] Electric Field
%
KfnQPdb= "E < ./SAVE/ndb.QP"
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The point is that the resulting spectra changes so greatly when the variable "BDmRange" changes. I think this is very strange. So, could you please tell me the reason for this great change? Does it have something to do with the dense of the K-point mesh in DFT calculation?
Thank you so much!

[Daniele Varsano]

Dear Wei Wei,

The point is that the resulting spectra changes so greatly when the variable "BDmRange" changes. I think this is very strange. So, could you please tell me the reason for this great change?

To me, the spectra is not changing at all. You have as a result of the calculation excitations energies and oscillator strength, and you DO NOT have peak width, so
in order to build up the spectra you are adding a Lorentzian width by hand to each peak. The smaller the Damping (BDmRange) the bigger will be the resolution. Most of the times in order to compare with experimental results, that have a REAL bandwidth, it is useful to tune your width.
Best,
Daniele

[WEI Wei]

Dear Daniele,
Thank you very much for your reply!