Yambo Community Forum

Posted: **Mon Mar 09, 2020 1:16 pm**

Dear Daniele,

I do not which claim of Andrea you are referring

I was referring to the https://www.materialscloud.org/learn/vi ... yambo-code

At the start, he mentioned the foregoing point.

A3: It is not created, because it is calculated for all the q by default. Have you tried?

In the following output for r-file, I copied the last part... the calculation is currently running, but it is at the q1 so, will it go for all the q-points? Earlier it computed the screening for all the q-points in the static dielectric calculations. Again, I just want the optical absorption so why do all the q-points calculating in this process?

Code: Select all

[06.02] BSE - Independent Particles absorption @q1
  ==================================================

  [RD./SAVE//ndb.dipoles]-------------------------------------
   Brillouin Zone Q/K grids (IBZ/BZ):  40   72   40   72
   RL vectors                   (WF):  5353
   Fragmentation                    :yes
   Electronic Temperature        [K]: 300.1000
   Bosonic    Temperature        [K]: 300.1000
   X band range           :   50   350
   X band range limits    : 160  161
   X e/h energy range [ev]:-1.000000 -1.000000
   RL vectors in the sum  :  5353
   [r,Vnl] included       :yes
   Bands ordered          :yes
   Direct v evaluation    :no
   Field momentum norm    :0.1000E-4
   Approach used          :G-space v
   Dipoles computed       :R V P
   Wavefunctions          :Perdew, Burke & Ernzerhof(X)+Perdew, Burke & Ernzerhof(C)
  - S/N 007524 -------------------------- v.04.05.00 r.09122 -

  [06.03] BSE Kernel @q1 (Resonant CORRRELATION EXCHANGE)
  =======================================================

  [BSE] Exchange components :  5353
  [RD./SAVE//ndb.BS_Q1_CPU_0]---------------------------------
   Brillouin Zone Q/K grids (IBZ/BZ):  40   72   40   72
  *WRN* RL vectors                   (WF):  67521
   Coulomb cutoff potential         :none
  *ERR* Parallel CPUs                    :2.1
   Parallel Roles                   :eh.k
  - S/N 007524 -------------------------- v.04.05.00 r.09122 -

   [06.03.01] Screened interaction header I/O
   ==========================================

   [RD./SAVE//ndb.em1s]----------------------------------------
    Brillouin Zone Q/K grids (IBZ/BZ):  40   72   40   72
    RL vectors                   (WF):  5353
    Coulomb cutoff potential         :none
    Fragmentation                    :yes
    Electronic Temperature        [K]: 300.1000
    Bosonic    Temperature        [K]: 300.1000
    Static diel. fun.  energies      :Perdew, Burke & Ernzerhof(X)+Perdew, Burke & Ernzerhof(C)
                       wavefunctions :Perdew, Burke & Ernzerhof(X)+Perdew, Burke & Ernzerhof(C)
    Global Gauge                     :length
    X matrix size          :  695
    X band range           :   50   350
    X e/h energy range [ev]:-1.000000 -1.000000
    X Time ordering        :R
    X xc-Kernel            :none
    X Drude frequency      : 0.00      0.00    
    X poles           [o/o]: 100.0000
    RL vectors in the sum  :  5353
    [r,Vnl] included       :yes
    Field direction        :0.5774E-5 0.5774E-5 0.5774E-5
    BZ energy Double Grid  :no
    BZ energy DbGd points  :0
    BZ Q point size factor : 1.000000
   [RD./SAVE//ndb.em1s_fragment_1]-----------------------------
    :: Current Q-pt index     : 1
    :: X energy range     [ev]: 0.00      0.00    
    :: X damping range    [ev]:  0.10000   0.10000
    :: Number of frequencies  : 1
   - S/N 007524 -------------------------- v.04.05.00 r.09122 -
   [WF-BSK] Performing Wave-Functions I/O from ./SAVE

   [FFT-BSK] Mesh size:  15   45   15

   [WF-BSK loader] Normalization (few states)  min/max  :0.405E-09 0.998    


   [06.03.02] Wave-Function Phases
   ===============================

   [BSE] WF phases found  [o/o]: 90.00000
   [WR./SAVE//ndb.BS_Q1_CPU_0]---------------------------------
    Brillouin Zone Q/K grids (IBZ/BZ):  40   72   40   72
    RL vectors                   (WF):  5353
    Coulomb cutoff potential         :none
    Parallel CPUs                    :20.1
    Parallel Roles                   :eh.k
    Fragmentation                    :no
    BS kernel          wavefunctions :Perdew, Burke & Ernzerhof(X)+Perdew, Burke & Ernzerhof(C)
    Static diel. fun.  energies      :Perdew, Burke & Ernzerhof(X)+Perdew, Burke & Ernzerhof(C)
                       wavefunctions :Perdew, Burke & Ernzerhof(X)+Perdew, Burke & Ernzerhof(C)
    BSK|Identifier              :  483
       |Dimension               :  66960
       |Bands                   : 130  190
       |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]:  5353
       |RL vectors [correlation]:  695
       |E/h energy range    [ev]:-1.000000 -1.000000
       |Coupling range     [o/o]: 100.0000  100.0000
     W |Interaction is diagonal :no
       |Matrix size             :  695
       |Bands                   :   50   350
       |e/h energy range    [ev]:-1.000000 -1.000000
       |Poles              [o/o]: 100.0000
       |RL vectors in the sum   :  5353
       |[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 007524 -------------------------- v.04.05.00 r.09122 -

Thanking you,

Posted: **Mon Mar 09, 2020 2:54 pm**

Dear Haseeb,

regarding Andrea statement, it looks to me rather bold. It is true that d-electrons require particular attention.
A3: I'm rather confused: what do you want to calculate? BSE requires the calculation of the screening for all the q points (see slide 10b in the cheatsheet) and this is obtained by setting the em1s (yambo -b). Next, the BSE matrix it is built for q=0 only (still the kernel requires the screening for all q points). We have also implemented BSE for finite q but at the moment it is not released under GPL version, so at the moment BSE (or any other calculation in transition space) can be performed for q=0 only.

Best,
Daniele

Posted: **Tue Jul 28, 2020 12:16 am**

Dear Yambo developers,

I found a paper (published in 2016), in which GW and BSE were done on top of DFT + U using Quantum ESPRESSO and Yambo!
here is the link:
https://iopscience.iop.org/article/10.1 ... 012040/pdf

My question is, is this feature made available in the official GPL release? If not, then can we also simply tweak the code to do that?

Regards,

Posted: **Tue Jul 28, 2020 8:16 am**

Dear Haseeb,

I've no idea what the authors did, I do suspect that the results are not reliable as the U term is not taken into account by Yambo and it is not subtracted, in this way the correlation is added both by U and by the GW self energy.
The p2y interface warns you about that, but probably the authors and reviewer, did not realise it.
What you can do is to calculate the BSE in top of DfT+U, provided that you consider a covariant approach for the calculation of the dipoles.
Best,
Daniele

Posted: **Wed Oct 06, 2021 8:06 am**

Dear Yambo Developers,

Is starting from DFT + U available in the latest version of Yambo for GW? or can we try it, if not rigorously tested so far!

Thanks,
Haseeb

Posted: **Wed Oct 06, 2021 8:16 am**

Dear Haseeb,
unfortunately this option is not yet available.
We are currently developing two different routes to allow this kind of calculation but none of the two are available at this moment.
Please note that the code should stop with an error in the p2y procedure, but in case it allows you to perform the calculation note that there is term missing in the QP evaluation.

Best,
Daniele

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