NAN correction in gw.qp file

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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haseebphysics1
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Re: NAN correction in gw.qp file

Post by haseebphysics1 » Sat Oct 02, 2021 9:07 pm

Daniele Varsano wrote: Mon May 06, 2019 6:18 am Dear Nannan Luo,
GW starting from HSE is not allowed at the moment. Different treatments of the divergence of the exchange term make Yambo and QE not compatible, resulting in a nonnegligible source of error. I have inserted barriers in p2y to prevent HSE use, but they have probably not yet percolated in the GPL release.
The allowed hybrid functionals at the moment are PBE0. We have recently also extended to the use of Gau-PBE, but I still have to push in the GPL release.
When using PBE0 (or HF), anyway particular care of the divergence treatment has to be considered, i.e., to use the same technique, which is "vcut_ws" or "vcut_spherical" in exxdiv_treatment and the corresponding use of the coulomb cutoff in Yambo with the same geometry.
Best,
Daniele

Dear Dr. Daniele,
I hope you are doing well!
Quoting one of your replies from this thread, I just wanted to ensure that I am taking all the needed parameters for the hybrid functional calculations (PBE0). However, I am working on a bulk system (so, no vacuum in any direction) with an orthorhombic system. So, I was wondering that I will not have to worry about the divergence treatments for small q vectors and variables like exxdiv_treatment (QE) and setting the column cutoff in Yambo! Am I correct?
And so, I would need to set only the functional type or set the number of q-vecs. In the QE input, and proceed as usual in Yambo.
Thanking you in advance,
Haseeb
Haseeb Ahmad
MS - Physics,
LUMS - Pakistan

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Daniele Varsano
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Re: NAN correction in gw.qp file

Post by Daniele Varsano » Tue Oct 05, 2021 9:32 am

Dear Haseeb,
exxdiv_treatment is mandatory in QE, so you need to use it.
My advise is to use the ws_cut both in QE and Yambo, converging it wrt the k points.
ws_cut tends to the bulk interaction for a large enough k point sampling.

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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