Yambo Community Forum

Posted: **Mon May 11, 2009 7:50 pm**

Dear Developers:

I performed the example supplied with CPC paper for bulk silicon using BSE calculation.
And I came to warnning message below:

Code: Select all

 <52s> [Haydock] Iteration 75 Accuracy :  0.05866|   0.0100
 <53s> [WARNING] [O_eels] Possible inaccuracy in the EPS prolungation
 <53s> [Haydock] Iteration 76 Accuracy :  0.05651|   0.0100
 <53s> [WARNING] [O_eels] Possible inaccuracy in the EPS prolungation

Is there any keyword to tune this situation ?

Another confusion is about output data given in o.eps_xxx or o.eel_xx. I noted there are 5 columns in the file and learned we generally deal with the 2nd and 3rd columns , but what are the fourth and fifth data ? I once found that there was no difference between 2nd and 4th columns or 3rd and 5th if a small damping parameter like 0.10 applied .

Best wishes,
Hai-Ping

Posted: **Mon May 11, 2009 8:49 pm**

Dear Hai-Ping,

The warning regards the eel, so you should worry only if you want to calculate it . Within the Tamm Dancoff approximation for the BSE, this spectra is obtained from the eps one, and a Kramers-Kronig has to be performed. In order for this transform to be accurate you should choose the energy range in such a way that the Im(eps) is (approx.) zero at the beginning and at the end of the range.

About the data in the o.eps_xxx or o.eel_xx:

Code: Select all

#
#  E/ev       e/Im       e/Re       eo/Im      eo/Re      e`/Im      e`/Re
#
   0.00000    0.03657    4.18331    0.03071    3.91715    0.03657    4.18331

The 2nd and 3rd column are the imaginary and real part of the calculated quantity, the 4th and 5th imaginary and real part of the same quantity but in the independent particle approximation, the last 2 columns should be there in the case of the Haydock procedure is used to solve the BSE and are the imaginary and real part of the calculated quantity at the n-1 iteration of the Haydock procedure (so they should be equal to the 2nd and 3rd column otherwise you need more iterations).

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Warning of EPS prolungation

Warning of EPS prolungation

Re: Warning of EPS prolungation