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Procedure to obtain phonon dispersion curve 
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Joined: Sat Mar 03, 2018 7:37 am
Posts: 75
University: IIIT Allahabad
Post Procedure to obtain phonon dispersion curve
Dear EPW experts,
I would like to know that how can I get the phonon dispersion curve data in epw calculation.I would like to see whether my wannier phonon dispersion data matches with the pw phonon data.Which card I need to add in epw.in file to see the phonon dispersion data.Please let me know.

Thanks and regards,
Anindya Bose
Research Fellow,
IIIT Allahabad


Mon Jul 09, 2018 8:19 am
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Joined: Wed Jan 13, 2016 7:25 pm
Posts: 573
University: Oxford
Post Re: Procedure to obtain phonon dispersion curve
Hello,

You need

band_plot = .true.

Then you need to provide the high symmetry path for the phonon on the fine grid with:
filqf = 'path.dat'

where "path.dat" contains your lists of q-points along the path you want.

Everything else can be false like:

elecselfen = .false.
phonselfen = .false.
a2f = .false.

Note that you can also get the electronic BS by doing
filkf = 'path.dat'

At the end of the calculations, you will get a file "band.eig" and "phband.freq".
They are in a format that allows you to use the q-e/bin/plotbands.x on those files to get them in gnuplot format.

Best,
Samuel

_________________
Dr. Samuel Poncé
Department of Materials
University of Oxford
Parks Road
Oxford OX1 3PH, UK


Mon Jul 09, 2018 9:19 am
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Joined: Sat Mar 03, 2018 7:37 am
Posts: 75
University: IIIT Allahabad
Post Re: Procedure to obtain phonon dispersion curve
Dear Sir,
If I want to see the phonon curve after a2f calculation ,then I must make a2f,elecselfen and Phonon self energy as true.In that case,won't I be able to find out phonon structure during a2f calculation?

Thanks and regards,
Anindya Bose


Mon Jul 09, 2018 11:27 am
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Joined: Wed Jan 13, 2016 7:25 pm
Posts: 573
University: Oxford
Post Re: Procedure to obtain phonon dispersion curve
You can do both. You will get the same phonon dispersion regardless.

For your 2D question, you will still have an issue even if ultra-dense grid are used if you are using 100x100x1 grids.
The problem is that the el-ph matrix element for small q will be wrongly interpolated. In 3D the matrix element diverge whereas in 2D they go to a finite value.

Best,
Samuel

_________________
Dr. Samuel Poncé
Department of Materials
University of Oxford
Parks Road
Oxford OX1 3PH, UK


Mon Jul 09, 2018 1:28 pm
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Joined: Sat Mar 03, 2018 7:37 am
Posts: 75
University: IIIT Allahabad
Post Re: Procedure to obtain phonon dispersion curve
Dear Sir,
Please have a look on this paper "Electron–Phonon Interactions and the Intrinsic Electrical Resistivity of Graphene" (link: https://pubs.acs.org/doi/abs/10.1021/nl ... ode=nalefd). This paper shows a2f epw calculation of 2D materials and it has been done in epw already.I am still waiting for a valuable comment from you in this regard.I am looking for some command using which a 2D calculation can be done here.

Thanks and regards,
Anindya Bose


Mon Jul 09, 2018 6:31 pm
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