[QE-users] ?==?utf-8?q? U calculation, different projection type

Thu Aug 27 10:01:11 CEST 2020

Dear Mona,

> I understand your point about the accuracy of ortho-atomic projector; but the stress and force calculations are not implemented in QE for this type of projection. Is there any way to get around this?

Now this is implemented in Quantum ESPRESSO 6.6. We have made developments and implementation for this case very recently and now all this is public. The manuscript is in preparation and will appear soon on arXiv.

Greetings,

Iurii

--
Dr. Iurii TIMROV
Postdoctoral Researcher
STI - IMX - THEOS and NCCR - MARVEL
Swiss Federal Institute of Technology Lausanne (EPFL)
CH-1015 Lausanne, Switzerland
+41 21 69 34 881
http://people.epfl.ch/265334
________________________________
From: users <users-bounces at lists.quantum-espresso.org> on behalf of Mona Asadinamin <Mona.a at uga.edu>
Sent: Wednesday, August 26, 2020 11:10:08 PM
To: Quantum ESPRESSO users Forum
Subject: Re: [QE-users] ?==?utf-8?q? U calculation, different projection type

Dear Iurii;

I understand your point about the accuracy of ortho-atomic projector; but the stress and force calculations are not implemented in QE for this type of projection. Is there any way to get around this?

Best regards;

Mona Asadi Namin
Graduate student
Center for simulational physics
University of Georgia
--------------------------------------
Email:mona.a at uga.ed<mailto:mona.a at uga.edu>u<mailto:mona.a at uga.edu>
Phone: +1-215-906-23-92

________________________________
From: users <users-bounces at lists.quantum-espresso.org> on behalf of Timrov Iurii <iurii.timrov at epfl.ch>
Sent: Wednesday, August 26, 2020 6:17 AM
To: Quantum ESPRESSO users Forum <users at lists.quantum-espresso.org>
Subject: Re: [QE-users] ?==?utf-8?q? U calculation, different projection type

[EXTERNAL SENDER - PROCEED CAUTIOUSLY]

Dear Antoine,

> As the resulting U are drastically different (>1eV),
> what is the criterium that we should use to decide wich is the "good" projector for a given system?

In Quantum ESPRESSO, two types of projectors are supported for DFT+Hubbard: "atomic" and "ortho-atomic". In other codes there are other projector types. So, for Quantum ESPRESSO, at present we can choose only between "atomic" and "ortho-atomic". Which one is better? From our experience, "ortho-atomic" seems to be better, but we are performing more extensive comparisons. It may also depend on the property you are interested in. Therefore, I would suggest to investigate both types of projectors (with they respective U (and V) values) for your system and see whether the results are similar or there are significant differences. But if you cannot do so, I would start with "ortho-atomic". As written here http://theossrv1.epfl.ch/Main/DFTHubbard :

"Ortho-atomic orbitals seem to provide more accurate results - maybe because if atomic (i.e. non-orthogonal) orbitals are used, the Hubbard correction can be added twice in the regions where orbitals overlap, or, when using the U alone, the orthogonalisation procedure makes the system more "aware" of the presence of the ligands (but, at the end, we think the most general approach is to use both U and V in a ortho-atomic formulation)."

HTH

Cheers,

Iurii

--
Dr. Iurii TIMROV
Postdoctoral Researcher
STI - IMX - THEOS and NCCR - MARVEL
Swiss Federal Institute of Technology Lausanne (EPFL)
CH-1015 Lausanne, Switzerland
+41 21 69 34 881
http://people.epfl.ch/265334
________________________________
From: users <users-bounces at lists.quantum-espresso.org> on behalf of Antoine Jay <ajay at laas.fr>
Sent: Wednesday, August 26, 2020 11:52:43 AM
To: Quantum ESPRESSO users Forum
Subject: Re: [QE-users] ?==?utf-8?q? U calculation, different projection type

Dear Iurii,
As the resulting U are drastically different (>1eV),
what is the criterium that we should use to decide wich is the "good" projector for a given system?

Regards,

Antoine Jay
LAAS-CNRS
Toulouse, France

Le Mercredi, Août 26, 2020 11:13 CEST, Timrov Iurii <iurii.timrov at epfl.ch> a écrit:

Dear Sergey,

As Lorenzo said, yes this is expected. Ab initio U depends on the Hubbard manifold, i.e. which projector functions are used (e.g. atomic, orthogonalized atomic, Wannier functions, you name it). So it is absolutely important to report in papers which projector functions were used for the calculation of U. In particular, this is why one should be very careful when comparing U values from different papers. There are also other factors that influence the value of U (pseudopotentials, oxidation state, functional, one-shot or self-consistent calculation). We have some papers in preparation on this topic, which hopefully would clarify a bit more these points. You can also check this web page: http://theossrv1.epfl.ch/Main/DFTHubbard

Greetings,

Iurii

--
Dr. Iurii TIMROV
Postdoctoral Researcher
STI - IMX - THEOS and NCCR - MARVEL
Swiss Federal Institute of Technology Lausanne (EPFL)
CH-1015 Lausanne, Switzerland
+41 21 69 34 881
http://people.epfl.ch/265334
________________________________
From: users <users-bounces at lists.quantum-espresso.org> on behalf of Lorenzo Paulatto <paulatz at gmail.com>
Sent: Wednesday, August 26, 2020 10:59:13 AM
To: users at lists.quantum-espresso.org
Subject: Re: [QE-users] U calculation, different projection type

> Is it expected behavior?

Yes,
kind regards

> Thanks,
>   Sergey

--
Lorenzo Paulatto - Paris
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