Initial layer position for 2D Coulomb truncation

Concerns issues with computing quasiparticle corrections to the DFT eigenvalues - i.e., the self-energy within the GW approximation (-g n), or considering the Hartree-Fock exchange only (-x)

Moderators: Davide Sangalli, andrea.ferretti, myrta gruning, andrea marini, Daniele Varsano

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Bo Peng
Posts: 9
Joined: Tue Feb 04, 2020 5:47 pm

Initial layer position for 2D Coulomb truncation

Post by Bo Peng » Mon Mar 07, 2022 6:32 pm

Ciao,

I am running the truncated Coulomb potential for 2D materials. If I change the initial position of the layer in QE, e.g. moving a graphene layer from z=0 to z=0.5 (in direct coordinate), the GW corrections have a difference about 5-15 meV. Is this something that I should worry about? Or I should just keep the atomic positions in z=0, as demonstrated in the tutorial on monolayer BN? Thank you in advance!

Best regards,
Bo
Bo Peng
PhD student in Physics
Cavendish Laboratory, University of Cambridge, UK

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Daniele Varsano
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Joined: Tue Mar 17, 2009 2:23 pm
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Re: Initial layer position for 2D Coulomb truncation

Post by Daniele Varsano » Mon Mar 07, 2022 7:07 pm

Dear Bo,
actually, this should not happen, and if I'm not wrong the potential component (ndb.cutoff) should be the same in the two cases, and the reason of the discrepancy should be ascribed to something else. Anyway, if you are not interested in extreme accuracy, the difference is rather small.
Also, we have developed a much better way to treat 2D systems, it will be released very soon and the actual 2D cutoff will be dismissed.

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/

Bo Peng
Posts: 9
Joined: Tue Feb 04, 2020 5:47 pm

Re: Initial layer position for 2D Coulomb truncation

Post by Bo Peng » Thu Mar 10, 2022 7:02 pm

Thank you Daniele! Look forward to the new release!
Bo Peng
PhD student in Physics
Cavendish Laboratory, University of Cambridge, UK

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