Yambo Community Forum

Dear Daniele,

I attached the report and log files of one of the bse calculation with the full diagonalization.
It seems working for more than 1 week, but still there is no progress. Does waiting any longer do any good?
Or do you have any suggestion (about parallelization or something else) to obtain results with this run?

Best

Dear Daniele,

The slepc solver works great, but it only prints the dielectric function.
However, when we apply cutoff in 2D system we need to obtain polarizabilities.
Is it possible to obtain alpha when we use slepc.

Best

Dear Fadıl,

slepc should also provide the alpha, can you post your input file?
About your previous run, your BSE matrix is large but still feasible with diagonalization, if it is stacked after 1 week it means something went wrong, but it is not easy to spot the reason.

Best,
Daniele

Dear Daniele,

Yes, you are right. When I change the input file it provide the alpha also.
Thank you!

Best

Xiaoming Wang wrote: ↑Tue Aug 10, 2021 4:22 pm Hi,

Another workaround, to get the exciton oscillator strength (transition dipole) I modified the code

Code: Select all

   ......
   ![--------------------------------------------
   n_elements=n_elements+1
   titles(n_elements)='dipole [Bohr^2]'
   !--------------------------------------------]
   Residuals(:) = real(BS_R(:)*conjg(BS_R(:)),SP)
   if (write_widths)  Residuals(:) = abs(BS_R(:))
   if(iq==1) q_norm=q0_def_norm**2
   if(iq> 1) q_norm=iku_v_norm(BSqpts(:,iq))**2
   ![--------------------------------------------------------------
   ! the oscillator strength
   dipol(:) = Residuals(:)/q_norm/(RL_vol/d3k_factor)
   !----------------------------------------------------------------]
   Residuals(:) = Residuals(:)*real(spin_occ,SP)/(2._SP*pi)**3*d3k_factor*4._SP*pi/q_norm*HA2EV
   .......
   ![------------------------------------------
   ! to print
   n_elements=n_elements+1
   rv(n_elements)=dipol(j2)
   !-------------------------------------------]

in ypp/excitons/excitons_sort_and_report.F.

Dear Xiaoming:
Thanks for your help!Could you know how to get the P_S^2 from the ypp?I changed the code based on your code,but the units of the P_S^2 let me confused!
Best wishes！
Quxiao

Dear all
please clarify my point that the strengths are reported in this file are in unit of 'eV' or unit of 'e.bohr'.



Maximum Residual Value = 0.99184E+00

E [ev] Strength Index

2.66076220 0.595841334E-8 1.00000000
2.66377698 0.432214064E-3 2.00000000
2.66379905 0.209940922E-2 3.00000000
2.66782112 0.966402438E-3 4.00000000
2.66784263 0.949996735E-3 5.00000000
2.67358023 0.143271606E-8 6.00000000
2.69463200 0.342101391E-3 7.00000000
2.69464556 0.317773602E-3 8.00000000
2.70601855 0.303304590E-3 9.00000000
2.70622099 0.104622693E-2 10.0000000
2.70629461 1.00000000 11.0000000
2.70630689 0.864063373E-1 12.0000000
2.83036681 0.881903188E-3 13.0000000
2.83045742 0.118884024E-2 14.0000000
2.83504518 0.601130605E-1 15.0000000
2.83513491 0.592793722E-1 16.0000000
2.86564469 0.115701542E-6 17.0000000

Dear Nilesh,

strengths are in Bohr, please note that they are normalized to the largest strength and renormalization factor is reported as Maximum Residual Value.

Best,
Daniele

Dear Daniele
Thank you very much for your reply and the important suggestion regarding renormalization. But I was reading in previous post that the reported oscillator strengths are formed as square modulus of Residual |R|^2. So if I am not wrong the final unit is bohr^2?

And my second question is that I am trying to calculate BSE transition dipole moment (\mu^2) so should i use this relation,

\mu^2 = |R|^2 * Direct volume of the lattice * N_k / 4 pi * spin

please correct me is there anything wrong?

Thank you

Dear Nilesh,

you are right, the strength is calculated as the square modulus.
About the prefactor, it should be correct, to be sure you can have a look at the epsilon expression in Eq.11a in the Yambo cheatsheet:
https://www.yambo-code.eu/wiki/images/c ... et-5.0.pdf

Best,
Daniele