Electron Distribution

[WEI Wei]

Dear developers,

Could you please tell me how to get the electron distribution of an excitonic state as the figure in attachment? Do I need a script to do the integration?
Thank you very much!

[Daniele Varsano]

Dear Wei Wei,
the integration is performed by yambo if you choose to do a 1D plot.
Cheers,

Daniele

[WEI Wei]

Dear Daniele,

Yes, I used "ypp -e w" and chose Direction= "1". In the resulting file of "o.exc_1d_2.xsf", it shows data as following:
# ||a1 [A]
#
-2.484906 0.582688
-2.248248 0.592906
-2.011591 0.608900
-1.774933 0.630969
-1.538275 0.662242
-1.301617 0.705489
-1.064960 0.750193
-0.828302 0.763074
-0.591644 0.715786
... ...
Then, I used these two volumes to draw the 1D electron distribution, but it gives a very ugly plot shown in attachment.


I still have another problem, I also used "ypp -e w" to plot a 2D electron distribution and use xcrysden to visualize it. But, I got a ugly picture again (shown on the left panel). So, how can I get a 2D picture like the on on the right panel?

Thank you very much!

[Daniele Varsano]

Dear Wei Wei
sorry but I do not understand what is your problem.
In order to plot 1d wfs, you do not need xsf format, but you can ask simply for gnuplot format.
As you know, the exc_wfs is a function of two variables: the position of the hole and electron, in order
to plot it the position of the hole have to be fixed, and the plot depends on where the hole is placed.
If you put the hole in a place were there is not charge, what you are looking at is just noise.
Try to play with 1D plot in order where the best place to put the holes, this is of course system dependent,
and depend on the position of your structure in the unit cell.
This is a study you have to make, we cannot help you on that.

Cheers,

Daniele

[WEI Wei]

Dear Daniele,

Thank you very much for your reply and patience!
I used "ypp -e w" below
-------------------------------------------------------------------------------------

wavefunction # [R] Wavefunction
excitons # [R] Excitons
Format= "g" # Output format [(c)ube/(g)nuplot/(x)crysden]
Direction= "1" # [rlu] [1/2/3] for 1d or [12/13/23] for 2d [123] for 3D
FFTGvecs= 11733 RL # [FFT] Plane-waves
States= "2 - 2" # Index of the BS state(s)
Degen_Step= 0.0100 eV # Maximum energy separation of two degenerate states
% Cells
5 | 5 | 1 | # Number of cell repetitions (even or 1)
%
% Hole
2 | 1 | 1.5 | # [cc] Hole position in unit cell
%
-------------------------------------------------------------------------------------
I got the file of "o.exc_1d_2". So, you mean I can treat this data file to obtain that electronic distribution?
Thank you very much.

[Daniele Varsano]

I got the file of "o.exc_1d_2". So, you mean I can treat this data file to obtain that electronic distribution?

This is a gnuplot format file you can easily visualize. What you call electron distribution is an excitonic
wave function with a fixed hole position. As this function depend on the hole position, be sure that your choice
is meaningful, and you are interested in the x direction.

Cheers,

Daniele

[WEI Wei]

Dear Daniele,
Thank you!

From “o.exc_E_sorted”, I read
---------------------------------------------
# E [ev] Strength Index
#
4.37 0.562E-12 1.00
4.71206 0.03150 2.00000
4.712 0.1644E-3 3.000
5.008 0.5765E-5 4.000
5.008 0.1469E-9 5.000
… …
1) So, the state indexed as 1.00 is a dark state, and the state indexed as 2.00000 is the first excitonic state. Am I right?

From “o.exc_weights_at_2”, I read
-------------------------------------------------------------------------------------------------
# Band_V Band_C K ibz Symm. Weight Energy
#
17.00000 20.00000 1.00000 1.00000 0.06923 4.69861
16.00000 20.00000 1.00000 1.00000 0.06922 4.69861
17.00000 20.00000 2.00000 4.00000 0.05291 4.72983
17.00000 20.00000 2.00000 2.00000 0.05291 4.72983
17.00000 20.00000 8.00000 2.00000 0.05291 4.72983
17.00000 20.00000 2.00000 3.00000 0.05290 4.72983
17.00000 20.00000 2.00000 1.00000 0.05290 4.72983
17.00000 20.00000 8.00000 1.00000 0.05290 4.72983
#
… …
2) So, these are the transitions contributing to this excitonic state. Am I right?

After the runlevel of “ypp –s w” with “QPkrange 1| 1| 17|20|, I got “o.sp_wf_k1_b17_3d.xsf”, “o.sp_wf_k1_b19_3d.xsf” and “o.sp_wf_k1_b20_3d.xsf”.
3) So, these three files are the wavefunctions of band 17, 19 and 20 at one K-point. Am I right?

Then, I used “ypp –e w” as follows
---------------------------------------------------------------------------
wavefunction # [R] Wavefunction
excitons # [R] Excitons
Format= "x" # Output format [(c)ube/(g)nuplot/(x)crysden]
Direction= "123" # [rlu] [1/2/3] for 1d or [12/13/23] for 2d [123] for 3D
FFTGvecs= 11733 RL # [FFT] Plane-waves
States= "2 - 2" # Index of the BS state(s)
Degen_Step= 0.0100 eV # Maximum energy separation of two degenerate states
% Cells
5 | 5 | 1 | # Number of cell repetitions (even or 1)
%
% Hole
2.000 | 1.000 | 1.500 | # [cc] Hole position in unit cell
%
---------------------------------------------------------------------------
I put a hole on a C-C bond, and the state was set as “States= "2 - 2" # Index of the BS state(s)”.
4) So, I want to know is this “Index” in the variable “States” the same as that in “o.exc_E_sorted”?

Thank you very much!

[Daniele Varsano]

Dear Wei Wei,

So, the state indexed as 1.00 is a dark state, and the state indexed as 2.00000 is the first excitonic state. Am I right?

No, and excitonic state can be bright or dark, in your case the first one is dark, and the second is bright.

So, these are the transitions contributing to this excitonic state. Am I right?

Yes, if you read carefully the header of the file there is written:
Electron-Hole pairs that contributes to Excitonic State xx more than yy,
What is unclear in this sentence?

So, these three files are the wavefunctions of band 17, 19 and 20 at one K-point. Am I right?

Yes, it should be self explaining, you have in output what uyou asked in input, right?
4) So, I want to know is this “Index” in the variable “States” the same as that in “o.exc_E_sorted”?
Why should be different?

Please, let me invite you to read carefully the documentations and study the tutorials, and if you have some doubts,
do not hesitate to write in the forum, but before doing that, please search in the forum if the question/problem have
been already solved/answered.

Cheers,

Daniele

[WEI Wei]

Dear Daniele,

OK, I see.
I really appreciate that you helped me so much!