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Weight of excitation
Posted: Thu Dec 19, 2019 2:19 am
by xtbu
Dear developers,
I am wondering about the wieght in ypp output inducing from ypp -e a as:
Code: Select all
# Band_V Band_C K ibz Symm. Weight Energy
#
32.0000 33.0000 12.0000 6.0000 0.1080 1.4859
32.0000 33.0000 12.0000 5.0000 0.1080 1.4859
32.0000 33.0000 12.0000 4.0000 0.1080 1.4859
31.00 34.00 12.0 6.000 0.6421E-1 1.506
31.00 34.00 12.0 5.000 0.6419E-1 1.506
31.00 34.00 12.0 4.000 0.6419E-1 1.506
If I want to konw the contributions of the trasition, like 32-33 as above, I need to count the contribution 0.108x3 or just 0.108?
An other thing is the total weight are not equal 1, far less than 1. Why?
Thanks!
xt Bu
Re: Weight of excitation
Posted: Thu Dec 19, 2019 3:18 pm
by Davide Sangalli
Dear Xiangtian Bu,
you should count 0.108x3
The total weight is not 1 because, in the output are reported only the weights of the most relevant transitions.
There is a default threshold at 5% of the total weight. You can lower the threshold via the variable "Weight_treshold"
Best,
D.
Re: Weight of excitation
Posted: Thu Dec 19, 2019 6:28 pm
by Daniele Varsano
Dear Xiangtian Bu,
the variable controlling the threshold of the transition printed in the output is "MinWeight" that will be substituted with "Weight_treshold" in the next release.
Best,
Daniele
Re: Weight of excitation
Posted: Fri Dec 20, 2019 9:36 am
by claudio
Dear Xiangtian Bu,
probably the name Weight is not so correct, it should be better to call it "percentage contribution" to the exciton
best
Claudio
Re: Weight of excitation
Posted: Mon Apr 27, 2020 10:38 am
by xtbu
Thanks, Davide, Daniele and Claudio,
So is the weight stands for |A_eh|^2？Where the A is the prefactor of |S>?
Thanks!
Xiangtian
Re: Weight of excitation
Posted: Mon Apr 27, 2020 11:22 am
by Daniele Varsano
Dear Xiangtian,
yes, the weight is defined as you indicated.
Best,
Daniele
Re: Weight of excitation
Posted: Thu May 21, 2020 10:39 am
by xtbu
Dear all,
I got the exciton dipoles as described here"
http://www.yambo-code.org/wiki/index.ph ... e_excitons".
And it is |A_eh<e|D|h>|, and whose square is proportional to oscillator strength. And I obtained the dipoles through Residuals as decroced here as :
Res=8pi/(q^2\Omega Nq)*|BS_R|^2. But why the two method has a different value of dipoles? I think |A_eh<e|D|h>|^2 should be equal as |BS_R|^2 here.
Thanks!
Xiang tiang
Re: Weight of excitation
Posted: Thu May 21, 2020 11:07 am
by Daniele Varsano
Dear Xiang,
I'm not sure I've understood your question,
I think |A_eh<e|D|h>|^2 should be equal as |BS_R|^2 here.
This is correct, these are the weighted transition dipoles, and the residuals are defined as you say, by multiplying them by a prefactor.
Maybe can be useful to look at this
thread.
Best,
Daniele
Re: Weight of excitation
Posted: Wed Aug 17, 2022 7:22 am
by pyadav
Dear team Yambo,
How can I get a rough estimate of the size/radius of the lowest energy exciton in any material after BSE calculation.
Thank you,
Pushpendra
Re: Weight of excitation
Posted: Wed Aug 17, 2022 10:03 am
by Daniele Varsano
Dear Pushpendra,
you can have an estimation by plotting the corresponding exictonic wave function, e.g. in 1D where the two other dimensions are averaged and then fit the envelope function with a hydrogenic wave function in the case it applies.
Best,
Daniele