Yambo Community Forum

Dear all,

I would like to study a magnetic material including Hubbard U. However, when performing the SCF calculation with Quantum ESPRESSO, I encounter an error indicating that the ONCV pseudopotentials do not contain atomic wavefunctions, which prevents the use of Hubbard U. On the other hand, for subsequent Yambo calculations, only ONCV pseudopotentials are supported.Does this mean that it is not possible to include Hubbard U in Yambo-based GW/BSE calculations?

If there is a way to include Hubbard U, could you please provide detailed guidance on how to implement it?

I appreciate any guidance and tutorial on that!
Best,
sunxl

Dear Sunxl,

some comments concerning your post:

• * while some ONCV pseudopotentials do not have atomic wavefuncitons,
  one can try to regenerate them using a newer version of the ONCV code which enables the
  user to print pseudo-atomic wavefunctions in UPF format
  * besides this, newly (re)generated ONCV psps may already have the atomic wfcs
  * Yambo supports norm-conserving pseudopotentials, not only ONCV (though ONCVs, eg from SG15 table, are often
  an excellent psp choice)
  * Once you manage to have a working non-conserving calculation at the DFT level, if one comes to yambo I think an error is triggered
  since a specific treatment of the +U potential is needed
  * This is currently under testing and requires (in its current implementation) to reconstruct the ionic pseudopot in yambo in order to
  avoid computing vxc (not yet available in the current release)

take care
Andrea

Dear Andrea,

Thank you very much for your detailed reply. Based on your explanation, my understanding is as follows, and I would like to kindly ask you to confirm whether it is correct:

1、Even if I switch to a newer version of ONCV pseudopotentials that include atomic wavefunctions, in the current public releases of Yambo it is still not possible to perform GW / BSE / SHG calculations that consistently and rigorously include the Hubbard U correction. Is this correct?

2、You mentioned that Yambo supports norm-conserving pseudopotentials beyond ONCV. If other types of norm-conserving pseudopotentials are used instead, can the reliability of subsequent GW / BSE / SHG calculations be ensured (in particular for magnetic materials)?

3、Regarding the recently released Lumen 2.0: does it support calculations including Hubbard U at the GW / BSE or nonlinear-optical (e.g. SHG) level?

Thank you very much for your time and clarification.

Best regards,
sunxl

Dear Sunxl,

1. It is possible to perform BSE calculation on top of DFT+U, while GW calculations are under testing. Depending on the release of Yambo p2y could stop with an error message that can be overcome, this is a barrier that will be removed once also the GW calculation will be officially released. In case you are interested in BSE only we can help in setting up the calculation.

2. Yes, Yambo supports norm-conserving calculations in general. ONCV anyway are particularly suitable as they require a lower kinetic energy cutoff respect to older psp.

3. As far as I know, the situation is the same. BSE are allowed, GW is under testing.

Best,

Daniele