Yambo Community Forum

hi 2 all,
1) In the Absorption or the EELS output files,
there are
E/ev[1] e/Im[2] e/Re[3] eo/Im[4] eo/Re[5]
i think this integer in the bracket is column number .
What is eo stands for ???
and is the e/Im[2] stands for imaginary espilon and e/Re[3] stands for real part of dielectric constant ????
any link or file where i can get such explaniation of output files.

thnaks
tc
dev

devsharma wrote: E/ev[1] e/Im[2] e/Re[3] eo/Im[4] eo/Re[5]
i think this integer in the bracket is column number .

yes

devsharma wrote: What is eo stands for ???

non interacting dielectric function

devsharma wrote: and is the e/Im[2] stands for imaginary espilon and e/Re[3] stands for real part of dielectric constant ????

yes

devsharma wrote: any link or file where i can get such explaniation of output files.

Ask here and we will try to help you.

Dear Andrea sir,

I Tried to repeat the paper
" Akira Tonomura, Junji Endo, Hajime Yamamoto, Katsuhisa Usami, Electron energy loss spectra of Rare earth orthovandates RVO4 (R=Sc,Y,la,Eu and Gd), Journal of Physical SOciety of JApan, 1978"

but when i plot the the dilectric constant of YVO4 (with and without Local field), I am getting the graph as ok with a plasmon energy at 24 eV (true, but in the assumption that reflectivity is inversly proportional to the fourth power of reflectivity above 25eV) whereas it is at 14 eV. The problem is that i am getting real part of epsilon as nageative over a range. And The eels spectra is flat in the range of 0-10eV, where in this region there are peaks due to interband transitions. The graph and input/output files are here atttached.

Please help and guide here,
thanks
take care

devsharma wrote: I am getting the graph as ok with a plasmon energy at 24 eV (true, but in the assumption that reflectivity is inversly proportional to the fourth power of reflectivity above 25eV) whereas it is at 14 eV.

Sorry dev, but this sentence does not make sense ! So how can I help you if I do not understand what you mean ?

devsharma wrote: The problem is that i am getting real part of epsilon as nageative over a range. And The eels spectra is flat in the range of 0-10eV, where in this region there are peaks due to interband transitions.

Ok, and where is the problem ?

Andrea

Hi Dev,

devsharma wrote: but when i plot the the dilectric constant of YVO4 (with and without Local field), I am getting the graph as ok with a plasmon energy at 24 eV (true, but in the assumption that reflectivity is inversly proportional to the fourth power of reflectivity above 25eV) whereas it is at 14 eV.

Well, you see a peak at about 14.5 eV, where Re[eps] = 0, which to me looks like the plasmon frequency, so I would be happy enough.
You cannot trust anything happening over 20eV since your maximum conduction band energy is at 20eV. You need more bands to see higher energy peaks properly.

The problem is that i am getting real part of epsilon as nageative over a range.

Why is that a problem?!

And The eels spectra is flat in the range of 0-10eV, where in this region there are peaks due to interband transitions.

No - the eels shows weak features (just like the experiment! Don't be lying now! ) They are just much smaller than the plasmon peak intensity. You might be able to relate the peaks in the eels at low energy with the peaks (more clear) in Im[eps]; also a smaller broadening will bring the peaks out more.

However: for the lower energy structures, you need a lot more k-points to converge the spectra (just do convergence tests on Im[eps]). If you want to reproduce both the high and low energy features, you need large k-point sets and large number of bands (enough to enclose the energy you want) - so you might want to do two calculations separately (large k set for low energy, less bands; more bands, small k set for high energy). Anyway, this depends on the memory that is needed, perhaps you can do it all in one go.

Regards,
Lord Conor

Hi,
Thanks Conor sir,
Actually, I was somewhat confused about definition of plasmon frequency but it is at Re[eps]=0 with positive slope.
Sorry 4 that.
Sir,I will implement your suggestions also
take care
with regards
Dev

Actually I just noticed now the eps_1, eps_2 data in the paper. Your calculation is already giving peaks at about 4.5 and 9 eV, close to the experiment, which is not bad at all for a rough RPA calculation. But at the end of the day you have to decide yourself what precision you want (is the band gap greatly underestimated?) and what level of theory you require, based on what information you want to derive from the data.
Cheers,
Conor