Ypp bug while analyzing excitons

Anything regarding the post-processing utility (e.g. excitonic wavefunction analysis) is dealt with in this forum.

Moderators: Davide Sangalli, andrea marini, Daniele Varsano

Post Reply
User avatar
wachr
Posts: 32
Joined: Wed Sep 24, 2014 4:43 pm

Ypp bug while analyzing excitons

Post by wachr » Wed Mar 29, 2017 9:58 am

Dear Yambo developers,

I am using ypp -e s for sorting the excitons and ypp -e a for obtaining their amplitude (still from the 3.4.2 suite, the old-fashioned version ;)). During the calculation, I provided band manipulation parameters (scissor, stretching of VB and CB).

I found that the amplitudes obtained are not consistent with the underlying RPA-spectrum, as the band manipulations are not applied. When I manually apply the band manipulation, things become more consistent:

The first, optically active exciton (straight line) vs. the contribution of the electronic states: As the exciton is strongly bound, these should not be the respective states.
o-run_10_BSE_diag.exc_spec_log_1_uncorrected.png
The first, optically active exciton (straight line) vs. the contribution of the electronic states with band manipulations: This looks much better now.
o-run_10_BSE_diag.exc_spec_log_1_corrected.png
The contribution of the electronic states relevant for the first exciton to the RPA-spectrum: It even looks consistent.
o-run_10_BSE_diag.rpa_spec_log_1_corrected.png
I think that band manipulation should be applied by ypp automatically at this point. (Or: does one have to supply the manipulation parameters again as they are only stored in the yambo-input?). The "problem": Valence and conduction band are stretched differently, which cannot be easily restored after the anaqlysis.

Kind regards!
Christian Wagner

P.S. My ypp-inputfile

Code: Select all

# | excitons                     # [R] Excitons
# | amplitude                    # [R] Amplitude
# | BoseTemp=  0.02585     eV    # Bosonic Temperature
# | States= "28 - 28"           # Index of the BS state(s)
# | Degen_Step= 0.000000   eV    # Maximum energy separation of two degenerate states
And my BSE inputfile

Code: Select all

optics                       # [R OPT] Optics
bse                          # [R BSE] Bethe Salpeter Equation.
bsk                          # [R BSK] Bethe Salpeter Equation kernel
bss                          # [R BSS] Bethe Salpeter Equation solver
em1s                         # [R Xs] Static Inverse Dielectric Matrix
rim_cut                      # [R RIM CUT] Coulomb interaction
NonPDirs= "XY"               # [X/BSS] Non periodic chartesian directions (X,Y,Z,XY...)
Chimod= "Hartree"            # [X] IP/Hartree/ALDA/LRC/BSfxc
BSEmod= "causal"             # [BSE] resonant/causal/coupling
BSKmod= "SEX"                # [BSE] IP/Hartree/HF/ALDA/SEX
BSSmod= "d"                  # [BSS] (h)aydock/(d)iagonalization/(i)nversion/(t)ddft`
WRbsWF                       # [BSS] Write to disk excitonic the FWs
BSENGexx=  40000       RL    # [BSK] Exchange components
BSENGBlk=  611         RL    # [BSK] Screened interaction block size
#WehCpl                      # [BSK] eh interaction included also in coupling

RandQpts= 0                  # [RIM] Number of random q-points in the BZ
RandGvec= 1            RL    # [RIM] Coulomb interaction RS components
CUTGeo= "cylinder z"         # [CUT] Coulomb Cutoff geometry: box/cylinder/sphere
CUTradius=18.4000            # [CUT] [au] Sphere/Cylinder radius
CUTCylLen=0.0                # [CUT] [au] Cylinder length

% KfnQP_E
 1.2317 | 1.0599 | 1.1479 |  # [EXTQP BSK BSS] E parameters  (c/v) eV|adim|adim
%
% KfnQP_Wv
 0.00     | 0.00     | 0.00     |        # [EXTQP BSK BSS] W parameters  (valence) eV|adim|eV^-1
%
% KfnQP_Wc
 0.00     | 0.00     | 0.00     |        # [EXTQP BSK BSS] W parameters  (conduction) eV|adim|eV^-1
%
KfnQP_Z= ( 1.000000 , 0.000000 )       # [EXTQP BSK BSS] Z factor  (c/v)
% BEnRange
  0.00000 | 10.00000 | eV    # [BSS] Energy range
%
% BDmRange
  0.012500 |  0.02500 | eV    # [BSS] Damping range
%
BEnSteps= 200                # [BSS] Energy steps
% BLongDir
 0.000000 | 0.000000 | 1.000000 |        # [BSS] [cc] Electric Field
%
% BSEBands
   55 | 74 |                 # [BSK] Bands range
%
% BndsRnXs
   1 | 256 |                 # [Xs] Polarization function bands
%
NGsBlkXs=  611         RL    # [Xs] Response block size
% LongDrXs
 0.000    | 0.000    |0.1000E-4 |        # [Xs] [cc] Electric Field
%
You do not have the required permissions to view the files attached to this post.
Christian Wagner
Institute of Physics
Chemnitz University of Technology, Germany

User avatar
Daniele Varsano
Posts: 4198
Joined: Tue Mar 17, 2009 2:23 pm
Contact:

Re: Ypp bug while analyzing excitons

Post by Daniele Varsano » Wed Mar 29, 2017 1:55 pm

Dear Christian,
actually this is not strictly speaking a bug, we are aware of that and at the moment ypp takes into account Kohn-Sham eigenvalues only.
As you argued the scissor/stretching parameters are not stored so they are only present in the input file.
Thanks for reporting, and we hope we will find the time soon to takes them into account.

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/

User avatar
wachr
Posts: 32
Joined: Wed Sep 24, 2014 4:43 pm

Re: Ypp bug while analyzing excitons

Post by wachr » Wed Mar 29, 2017 4:20 pm

Dear Daniele,

thank you very much for your positive reply!

Kind regards,
Christian
Christian Wagner
Institute of Physics
Chemnitz University of Technology, Germany

Post Reply