Exciton spatial distribution

[WangFuyou]

Dear yambo developers，
After doing the BSE calculation, I try to get the spatial distribution of excitons with ypp. But there is a problem with the results of importing VESTA. Also, I found a sentence on https://www.yambo-code.eu/wiki/index.ph ... 022_school website,
“A non-trivial input parameter is the hole position. The best position for the hole is where the valence electrons contributing to the exciton are localised. In the case of hBN, they are on the nitrogen atoms.”
But I'm a little confused about how we're supposed to know the location of the valence electrons that contribute to the exciton.
I am looking forward to your answer. I would appreciate it.

Yours，
WangFuyou

[Daniele Varsano]

Dear WangFuyou,

what kind of problem you are experiencing using VESTA, if you chose the option xsf format both Vesta and XcrysDen should be able to visualize it.
About the hole position, which is anyway unrelated with your problem. Performing an analysis of the exciton in terms of contribution of electron-hole pairs (ypp -e a option) you can individuate the valence bands (number of band and k point) contributing the most and then visualize them both using QE or ypp (ypp -s w).

Best,
Daniele

[WangFuyou]

Dear Daniele，
Thank you for your reply. In addition, I am following the tutorial on this site to analyze the exciton function, but I do not know how to get the background diagram in this color in the tutorial ( the last figure in https://www.yambo-code.eu/wiki/index.ph ... e_excitons). My graph is similar to the last figure in https://www.yambo-code.eu/wiki/index.ph ... 022_school, where the spatial distribution of excitons appears to be around some atoms, and how do I color it across the space.

yours,
WangFuyou

[Daniele Varsano]

Dear WangFuyou,

the two plot you are indicating have different format with a different way to represent the data. The first one is build from 2D data were the value along the z direction were integrated (you can ask for in this in the ypp input), then the plot is a color map done with xcrysden, you can choose what kind of color scheme to use among a few, this should be RGB or something similar. The second plot is an isosurface of a 3D map, and the surface corresponding to a chosen value is displayed.

Best,

Daniele

[WangFuyou]

Dear Daniele，
Thank you for your reply. I'm not sure if I'm doing this right, I've already selected Direction= "12" in the input file. I think the output should be 2D, but the result after visualization is still 3D. I uploaded my input file hoping to get answers.

Yours,
WangFuyou

[Daniele Varsano]

Dear WangFuyou,

if you do a grep of the xsf file:

> grep BEGIN_BLOCK_DATAGRID file.xsf

what do you find, 2D or 3D?

Best,
Daniele