Hubbard parameter

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)

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8813204602
Posts: 58
Joined: Tue Jun 15, 2021 5:53 pm

Hubbard parameter

Post by 8813204602 » Wed Feb 09, 2022 8:18 pm

Dear Yambo developer,

I read in the forum that GW on top of DFT+U is not implemented in yambo. I have a number of questions in this regard:

1) For systems containing d electrons such as nickel, are the results acceptable if I perform calculations of optical and magneto-optical properties by GW on top of DFT (without U)?

2) I found a paper, in which GW had been done on top of DFT + U using BerkeleyGW, but this point had been also mentioned:
In our G0W0 calculations, we will treat on the same footing the Hubbard potential (Vhub) and the LSDA exchange-correlation potential V LSDA (xc) . That is, the self-energy correction is given by:
ΔΣ = Σ − V LSDA(xc) − V(hub) ,
where Σ is the conventional self-energy operator in the GW approximation. In this way, the Hubbard potential, together with the LSDA exchange-correlation potential, have been subtracted from the quasiparticle energies corrections to avoid the double-counting issue
Is it possible to run GW on top of DFT+U in Yambo using this method?

Best,
Mitra Helmi
Mitra Helmi,Ph.D student
Ferdowsi university of Mashhad
Mashhad,Iran

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Daniele Varsano
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Re: Hubbard parameter

Post by Daniele Varsano » Thu Feb 10, 2022 9:06 am

Dear Mitra,

1) I have no experience, what you can do is to give a try and evaluate the accuracy, other option is to start by ground state calculated with hybrid functionals.
2) Yes, that's exactly the way to do it, and to apply it, the value <n|Vhub)|n> is needed. We are implementing it in these days and it will be ready very soon. Nevertheless I cannot say that it will be released in the next release that it will happen in few weeks, or the in the next one.

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/

8813204602
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Joined: Tue Jun 15, 2021 5:53 pm

Re: Hubbard parameter

Post by 8813204602 » Mon May 30, 2022 12:34 pm

Dear Daniele,

Is it possible to calculate GW on top of DFT+U using the new version 5.1?

Best,
Mitra
Mitra Helmi,Ph.D student
Ferdowsi university of Mashhad
Mashhad,Iran

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Daniele Varsano
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Re: Hubbard parameter

Post by Daniele Varsano » Mon May 30, 2022 3:07 pm

Dear Mitra,

unfortunately, the GW on top of DFT+U has not been yet released. We really hope to include it 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/

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Re: Hubbard parameter

Post by Dean » Fri Sep 30, 2022 3:02 am

Dear Daniele,

When is it possible to calculate GW on top of DFT+U using Yambo?

Best
Dr. Yimin Ding
Soochow University, China.

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Daniele Varsano
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Re: Hubbard parameter

Post by Daniele Varsano » Fri Sep 30, 2022 8:08 am

Dear Yimin,

the implementation has been done, but not yet tested so it has not been included in the current release.
I really hope we can include it in the next release that should appear in the next few months.

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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Re: Hubbard parameter

Post by pyadav » Fri Sep 30, 2022 3:57 pm

Dear team Yambo,

Can we calculate magneto-optic effects such as Kerr and Faraday rotations without DFT+U? I can see from the list of executables in yambo bin that there are {yambo_magnetic, yambo_kerr} executables.

What are the uses of these executables and can I find some tutorial or post in forum which I can follow?

Thank you,
Pushpendra
Pushpendra Yadav
Ph.D. Research Scholar
Quantum Transport and Theory Group
Department of Physics
Indian Instittute of Technology Kanpur, India.

https://sites.google.com/site/amitkag1/

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Davide Sangalli
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Re: Hubbard parameter

Post by Davide Sangalli » Mon Oct 03, 2022 9:09 am

Dear Pushpendra,
to compute magneto-optical properties:
  • up to 4.5, you need to use yambo_kerr and add the flag

    Code: Select all

    EvalKerr
    when running a BSE simulation.
  • Since version 5.0, you can just use the yambo executable and set the input variable

    Code: Select all

    BSEprop="abs kerr"
    to get both the magneto-optical properties and standard absorption.
Also, please notice that for DFT+U there is a barrier in the p2y converter, but you can comment it out in the code.
After that the code will run, but there are 2 issues to keep in mind
  • GW simulations do not subtract the U term from the hamiltonian before adding the self-energy. So, you would have some double counting between U and Sigma=GW
  • The dipoles, computed with the standard approach do not include the term [U,x]. You can however solve this by using other approaches for the dipoles (shifted grids or covariant dipoles
Especially if you have a magnetic system we advise to move to version 5.1 (or 5.0 at least)

Best,
D.
Davide Sangalli, PhD
CNR-ISM, Division of Ultrafast Processes in Materials (FLASHit) and MaX Centre
https://sites.google.com/view/davidesangalli
http://www.max-centre.eu/

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Re: Hubbard parameter

Post by pyadav » Wed Oct 19, 2022 8:04 pm

Dear David,

Thank you so much for your response.

Can you please clarify how to do the following
Also, please notice that for DFT+U there is a barrier in the p2y converter, but you can comment it out in the code.
After that, how to get rid of the following?
GW simulations do not subtract the U term from the hamiltonian before adding the self-energy. So, you would have some double counting between U and Sigma=GW
and where exactly to make any change for the shifted grid or covariant dipoles as said-

The dipoles, computed with the standard approach do not include the term [U,x]. You can however solve this by using other approaches for the dipoles (shifted grids or covariant dipoles
Also, how version 5.1 is different than 5.0 for GGA+U purposes?

Thank you,
Pushpendra
Pushpendra Yadav
Ph.D. Research Scholar
Quantum Transport and Theory Group
Department of Physics
Indian Instittute of Technology Kanpur, India.

https://sites.google.com/site/amitkag1/

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Daniele Varsano
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Re: Hubbard parameter

Post by Daniele Varsano » Thu Oct 20, 2022 9:05 am

Dear Pushendra,


1) in interface/p2y/mod_p2y.F
change line 909

Code: Select all

 if(pw_lda_plus_u) call error(' LDA+U. Hubbard correction is not considered in yambo.')
in

Code: Select all

 if(pw_lda_plus_u) call warning(' LDA+U. Hubbard correction is not considered in yambo.')
2) You cannot get rid at the moment, so you cannot do GW calculations on top of DFT+U but only BSE directly (eventually using some scissors)

3) E.g. in the dipole calculation set
DipApproach="Covariant"

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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