optical transition analysis

[Weiqing Zhou]

Hi all,

If I want to know that a peak contributed by which transitions, can yambo give corresponding information ?

Best,
Weiqing

[Daniele Varsano]

Dear Weiqing,
this can be done by using the ypp utility.

Code: Select all

ypp -e a 

to generate the input to choose the exciton you want to analyse, and then run ypp.
The BSE need to be solved by uncommenting the WRbsWF variable.
In order to select the excitation run ypp -e s first you will have the excitation energies and corresponding index.

Best,
Daniele

[Weiqing Zhou]

Dear Daniele,

Thanks!
But can I do this analysis for RPA optical absorption instead of BSE ?

Best,
Weiqing

[Daniele Varsano]

It can be done if the RPA is solved in transition space,

Code: Select all

yambo -o b -k hartree -y d

Best,
Daniele

[Weiqing Zhou]

Dear Daniele,

1. Why you say yambo -o b -k hartree -y d is a RPA one ? I think RPA optics should be yambo -o c.

when I use ypp -e a, I find input is :
--------------------------------------------------------------------------------
excitons # [R] Excitons
amplitude # [R] Amplitude
States= "1 - 1" # Index of the BS state(s)
#DipWeight # Weight the contribution to the exciton WFs with the dipoles
Degen_Step= 0.0100 eV # Maximum energy separation of two degenerate states
---------------------------------------------------------------------------------
2. What does 'States' mean ? the index of peak in absorption ? If I want to know the contribution of 2-nd peak, what should I set ?

3. the output files are o.exc_amplitude and o.exc_weights. What information do they contain ?

Actually, what I want to know is that a 1.3 eV peak is mainly contributed from what transitions.

Best,
Weiqing

[Daniele Varsano]

Dear Weiqing,

1. Why you say yambo -o b -k hartree -y d is a RPA one ? I think RPA optics should be yambo -o c.

Both are RPA calculated on a different basis (transitions vs reciprocal lattice vector). If you want to analyze your peak you need to perform calculations in the transition space.

What does 'States' mean ? the index of peak in absorption ?

No, it is the index of the excitation sorted by energies, you can have dark excitation you cannot see by looking at the spectra.
As stated above you need to sort your excitation by running:

Code: Select all

ypp -e s 

you will have as output two files with the excitation ordered by energy and by intensity, there you can identify your peak and see the corresponding index. This is the index you need to set in the ypp input.

the output files are o.exc_amplitude and o.exc_weights. What information do they contain ?

As reported in the header of the o.exc_weights file you have the transition that mostly contributes to that excitation, so what you are looking for.

For a step by step guide you can have a look at this tutorial:
http://www.yambo-code.org/wiki/index.ph ... e_excitons

Best,
Daniele