G0W0 calculations on double grid

Please post here any issue related to convergence parameters in linear response GW and BSE calculations.

Moderators: Davide Sangalli, Daniele Varsano

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mrefiore
Posts: 7
Joined: Thu Sep 12, 2019 6:55 pm

G0W0 calculations on double grid

Post by mrefiore » Mon Mar 01, 2021 1:10 pm

Dear YAMBO developers and users,

I'm currently trying to run a G0W0 calculation exploiting the double grid feature. I performed an nscf run on a dense grid (32x32x1) and in the coarse grid (9x9x1) SAVE I successfully created the ndb.DoubleGrid database. However, when I run the G0W0 calculation on the coarse grid, even though in the report and logfile I notice that YAMBO uses the fine grid I get a gap result that is extremely close (just 1 or 2 meV away) to the straightforward coarse grid calculation (without double grid).
What am I missing? I would expect a bigger impact of the double grid on the GW calculation. I also tried with a finer coarse grid (14x14x1) but the outcome did not change, the double-grid result is very close to the coarse one.
I'm attaching the input, report and logfiles of my calculations.
Thank you very much for your help!
Best,


Michele
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Michele Re Fiorentin, PhD
Center for Sustainable Future Technology CSFT@PoliTo
Italian Institute of Technology

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claudio
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Re: G0W0 calculations on double grid

Post by claudio » Mon Mar 01, 2021 11:00 pm

Dear Michele

I think this is due to the no correct treatment of the q=0 term,
that unfortunately the double-grid cannot solve.
You may have a look here:

How dielectric screening in two-dimensional crystals affects the convergence of excited-state calculations: Monolayer MoS2
Falco Hüser, Thomas Olsen, and Kristian S. Thygesen
Phys. Rev. B 88, 245309
https://core.ac.uk/download/pdf/192327286.pdf

maybe Daniele will add more comments on this point.

best
Claudio
Claudio Attaccalite
[CNRS/ Aix-Marseille Université/ CINaM laborarory / TSN department
Campus de Luminy – Case 913
13288 MARSEILLE Cedex 09
web site: http://www.attaccalite.com

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Daniele Varsano
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Re: G0W0 calculations on double grid

Post by Daniele Varsano » Tue Mar 02, 2021 9:21 am

Hi Michele,
indeed we have very decently developed a new technique to accelerate GW convergence for 2D materials. This development it is not yet merged in the official release, but it will merged soon.

Best,
Daniele
Dr. Daniele Varsano
S3-CNR Institute of Nanoscience and MaX Center, Italy
MaX - Materials design at the Exascale
http://www.nano.cnr.it
http://www.max-centre.eu/

mrefiore
Posts: 7
Joined: Thu Sep 12, 2019 6:55 pm

Re: G0W0 calculations on double grid

Post by mrefiore » Tue Mar 02, 2021 3:18 pm

Dear Claudio and Daniele,

thank you very much for your answers! I'm looking forward to the new release then!
Best,


Michele
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Michele Re Fiorentin, PhD
Center for Sustainable Future Technology CSFT@PoliTo
Italian Institute of Technology

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