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Questions about exciton-phonon interactions of h-BN

PostPosted: Fri Oct 12, 2018 9:42 am
by will
Hi all,
I'm very interested in Yambo's exciton-phonon realization.

Now I’m trying to reproduce the results of Prof. Marini’s paper titled “ab initio finite-temperature exciton”. For silicon, by following the tutorial on Yambo’s website, I have nicely reproduced the finite-temperature optical absorption spectra.

But for h-BN, after including exciton-phonon interactions the spectra redshift compared with frozen-atom BSE one as shown in the attached figure, which is opposite to Prof. Marini’s result.

I’m confused a lot. Is there something to be careful when doing calculations on exciton-phonon interactions? Below is some computational details,
LDA indirect bandgap: 4.03 eV, direct bandgap: 4.51 eV
For the electron-phonon calculations, I used 6*6*2 k-grid in scf and nscf calculation and 50 random q points in ph calculations.
For the bse calculations, I used 18*18*6 k-grid.

I also attached some input and output files. Could you please help me?

Thank you very much!

Best regards,
Xiaowei

Re: Questions about exciton-phonon interactions of h-BN

PostPosted: Thu Oct 25, 2018 9:17 am
by claudio
Dear Xiaowei

your results seem correct to me, instead, the behavior in the Marini paper is very strange.
Please have a look also to

https://journals.aps.org/prb/pdf/10.110 ... .89.085202

or

https://aip.scitation.org/doi/abs/10.1063/1.4927081

that performed similar calculations on other materials and found results similar to yours
best regards
Claudio Attaccalite

Re: Questions about exciton-phonon interactions of h-BN

PostPosted: Fri Oct 26, 2018 9:07 am
by will
Dear Claudio,
Thank you very much. I will carefully read the two papers.
Best regards
Xiaowei

Re: Questions about exciton-phonon interactions of h-BN

PostPosted: Sat Nov 10, 2018 8:09 am
by claudio
Dear Xiaowei

another calculation was performed with Yambo on hexagonal boron nitride,

https://arxiv.org/pdf/1811.01695.pdf

you can compare your results with them too

best
Claudio

Re: Questions about exciton-phonon interactions of h-BN

PostPosted: Wed Nov 14, 2018 9:05 am
by will
Dear Claudio
OK, thank you.
Xiaowei