BSE diago solver is not using excitonic WF

[ivona]

Dear developers,

I am running a BSE calculation using the diagonalisation solver (using the DFT wavefunctions from my /SAVE database combined with a scissor shift from my previous GW calculation) and I am accounting a worrying message in my report file. During the diagonalisation step it says following:

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[05] BSE solver(s)
 ==================


  [05.01] Diago solver
  ====================

  [RD./bii3_BSE//ndb.BS_diago_Q01]----------------------------
   BS kernel          energies      : Analyt. E
   BSK|Identifier              :  3827
      |Dimension               :  6144
      |Bands                   : 130  136
      |Exchange           [res]:yes
      |Correlation        [res]:yes
      |Kernel`s coupling       :no
      |Exchange           [cpl]:no
      |Correlation        [cpl]:no
      |W interaction is bare   :no
      |ALDA kernel in R-space  :no
      |RL vectors    [exchange]: 13379
      |RL vectors [correlation]:  417
      |E/h energy range    [ev]:-1.000000 -1.000000
      |Coupling range     [o/o]: 100.0000  100.0000
    W |Interaction is diagonal :no
      |Matrix size             : 1201
      |Bands                   :   1  290
      |e/h energy range    [ev]:-1.000000 -1.000000
      |Poles              [o/o]: 100.0000
      |RL vectors in the sum   : 25879
      |[r,Vnl] included        :yes
      |Field direction         :0.5774E-5 0.5774E-5 0.5774E-5
      |Coulomb Cutoff          :none
      |xc-Kernel               :none
   RIM|RL components      [col]:0
      |Random points      [col]:0
  - S/N 004521 -------------------------- v.04.03.03 r.00139 -
  *WRN* BSK Identifier                  :  3827
   Excitonic eigenstates included  :no
   Field direction                 :0.7071E-5 0.7071E-5  0.000
   Number of eigenstates included  :  6144
  - S/N 004521 -------------------------- v.04.03.03 r.00139 -

I am concerned about the lines:
*WRN* BSK Identifier : 3827
Excitonic eigenstates included :no

I assume this makes the absorption spectrum meaningless? How do i make sure that excitonic eigenstates are included in the calculation? Shall I add more BSEbands or does this have to do with the fact that I am not reading QP wavefunctions but a DFT wavefunctions and that I solely employ a scissor shift from my prior GW-calculation?

Thank you very much in advance!

[Daniele Varsano]

Dear Ivona,
welcome in the Yambo forum.
First, let me ask you to fill your signature with your complete name and affiliation: this is a rule of the forum and you can do once for all by filling the signature in your forum user profile.

Coming to your questions:

*WRN* BSK Identifier : 3827
Excitonic eigenstates included :no

Actually, they are two not related issues:

*WRN* BSK Identifier : 3827

This is warning Yambo emits as it recognizes after reading a previously stored database (note RD):
[RD./bii3_BSE//ndb.BS_diago_Q01
and it has a different ID of the current run, so most probably it was generated previously by considering a different SAVE directory. It is it not error as it is totally safe to consider different databases, but just a warning to check if everything is correct.

Excitonic eigenstates included :no

This simply means that after diagonalization the eigenstates of the BSE matrix are not stored in the database. This is the default. In case you need it (e.g. in order to compute real space excitonic wavefunction) you need to activate a keyword in the input file:

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WRbsWF

it appears by adding verbosity in the generation of the input file (-V resp or -V all) and need to be uncommented.

Best,
Daniele

[ivona]

Dear Daniele,

thank you so much for the prompt reply. I have added the extra keyword and indeed only changes the report-file while the spectrum stays the same. Now I feel more confident in running my benchmark.

Thanks again,
Ivona