Shifted grids for TDDFT dipoles

Deals with issues related to computation of optical spectra, in RPA (-o c) or by solving the Bethe-Salpeter equation (-o b). Includes local field effects, excitons, etc.

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MarcoC
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Joined: Wed Sep 30, 2009 3:16 pm

Shifted grids for TDDFT dipoles

Post by MarcoC » Mon Jul 13, 2020 12:18 pm

Dear Yambo developers,
I am trying to simulate the optical properties of a defective system which requires the use of a PBE+U approach for a reliable description of the ground state.

To deal with the dipole matrix elements I was thinking to use the approach referred as shifted grids in the yambo paper.
Unfortunately I faced some difficulties in understanding how to provide to yambo the correct database for the simulation.
Which is the correct procedure for providing to yambo the two meshes?
Should the original and shifted k-point mesh provided in a single database or in two separate databases?
Is there a particular order of the k-point to be respected while preparing the databases with the pw run?

Thank you very much for your support, best,
Marco

----------------------------
Dr. Marco Cazzaniga
PostDoc
Chemistry Department - Università degli Studi di Milano
Milan - Italy

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claudio
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Joined: Tue Mar 31, 2009 11:33 pm
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Re: Shifted grids for TDDFT dipoles

Post by claudio » Mon Jul 13, 2020 1:06 pm

Dear Marco

I advise you to use the Covariant approach. These dipoles are calculated
with the same k-point grid by finite differences, see the Yambo paper.

You can generate input with:

Code: Select all

yambo -o c -V resp
and then set

Code: Select all

DipApproach= "Covariant"
these dipoles are compatible with PBE+U

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
Freely download scientific books from: http://www.freescience.info

MarcoC
Posts: 2
Joined: Wed Sep 30, 2009 3:16 pm

Re: Shifted grids for TDDFT dipoles

Post by MarcoC » Tue Jul 14, 2020 7:28 am

Dear Claudio,
thank you very much for your suggestion, I will try the solution you proposed me,
Best,
Marco

----------------------------
Dr. Marco Cazzaniga
PostDoc
Chemistry Department - Università degli Studi di Milano
Milan - Italy

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Daniele Varsano
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Joined: Tue Mar 17, 2009 2:23 pm
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Re: Shifted grids for TDDFT dipoles

Post by Daniele Varsano » Tue Jul 14, 2020 11:07 am

Dear Marco,
just a minor warning, the "covariant" method at the moment cannot be used in GPU machines as Marconi100, but it will be ported in the next days.
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/

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