Yambo Community Forum

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

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

Dear Daniele,

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

Best,
Mitra

Dear Mitra,

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

Best,
Daniele

Dear Daniele,

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

Best

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

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

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.

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

Dear Pushendra,


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