[QE-users] U calculation, different projection type

[Timrov Iurii]

Dear Sergey,


> I have more general question - it seems that whole idea to use U correction if the system under study is metallic in plain DFT, and using DFT+U brings the system to the correct ground state. The system I study is a MOF with Mn atoms. It is already insulating (band gap ~1.8 eV from DFT), but I guess U correction will increase band gap even more. I wonder if I really need to use U correction. Unfortunately, the material is not well studied, and experimental paper does not provide much information about electronic structure - just geometry (cif) and ferroelectric properties are reported.


I am not familiar with DFT+U studies of MOFs, so I cannot comment much. Concerning DFT+U for band gaps, please see here: 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 Sergey Lisenkov <proffess at yandex.ru>
Sent: Wednesday, August 26, 2020 12:51:07 PM
To: Quantum ESPRESSO users Forum
Subject: Re: [QE-users] U calculation, different projection type

Dear Iurii, Lorenzo

Thanks for prompt reply.

I'll compare properties of the system I'm investigating, using both projection types.

I have more general question - it seems that whole idea to use U correction if the system under study is metallic in plain DFT, and using DFT+U brings the system to the correct ground state. The system I study is a MOF with Mn atoms. It is already insulating (band gap ~1.8 eV from DFT), but I guess U correction will increase band gap even more. I wonder if I really need to use U correction. Unfortunately, the material is not well studied, and experimental paper does not provide much information about electronic structure - just geometry (cif) and ferroelectric properties are reported.

Thanks,
 Sergey Lisenkov



26.08.2020, 12:14, "Timrov Iurii" <iurii.timrov at epfl.ch>:

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<mailto:users-bounces at lists.quantum-espresso.org>> on behalf of Lorenzo Paulatto <paulatz at gmail.com<mailto:paulatz at gmail.com>>
Sent: Wednesday, August 26, 2020 10:59:13 AM
To: users at lists.quantum-espresso.org<mailto: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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