[Wien] Hartree-Fock and the Hubbard Model

[delamora]

Dear Fabien Tran and Karel Vyborny,

Thanks for your comments.


What I want to know is if the Hartree Fock exchange is what the Hubbard U is trying to model

What I know is that for strong intraatomic repulsion, 3d and 4f, the Hubbard U gives good results, although the U is a parameter.

But for intermediate intraatomic repulsion, 4d, 5d, 5f then more expensive methods are needed, such as DMFT

So, if this is the case that the Hartree Fock exchange is what the Hubbard U is trying to model then the hybrid functionals would do a better job.

So, my question is; What are the Hubbard U and DMFT trying to model?

Cheers

          Pablo de la Mora


________________________________
De: Wien <wien-bounces at zeus.theochem.tuwien.ac.at> en nombre de delamora <delamora at unam.mx>
Enviado: martes, 25 de octubre de 2016 11:05:08 a. m.
Para: A Mailing list for WIEN2k users
Asunto: Re: [Wien] Hartree-Fock and the Hubbard Model

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Dear F Tran,

Thank you for your suggestion.

I found another one

http://www.wien2k.at/events/ws2015/Tran-talk_xc.pdf

It could be interesting, ja, ja (spanish accent)

I have not read them yet


Saludos


              Pablo

________________________________
De: Wien <wien-bounces at zeus.theochem.tuwien.ac.at> en nombre de tran at theochem.tuwien.ac.at <tran at theochem.tuwien.ac.at>
Enviado: martes, 25 de octubre de 2016 02:25:25 a. m.
Para: A Mailing list for WIEN2k users
Asunto: Re: [Wien] Hartree-Fock and the Hubbard Model

Hi,

all these methods are somehow based on the Hartree-Fock method,
which is (partially) free of self-interaction error.
The SIE with LDA/GGA is particularly large for localized d or f
electrons, such that LDA/GGA don't work well with these systems.

The onsite LDA+U and onsite hybrid are by far much cheaper than
the full hybrids.

This is a good paper to read:
http://journals.aps.org/prb/abstract/10.1103/PhysRevB.79.035103

F. Tran

On Tuesday 2016-10-25 02:09, delamora wrote:

>Date: Tue, 25 Oct 2016 02:09:24
>From: delamora <delamora at unam.mx>
>Reply-To: A Mailing list for WIEN2k users <wien at zeus.theochem.tuwien.ac.at>
>To: A Mailing list for WIEN2k users <wien at zeus.theochem.tuwien.ac.at>
>Subject: [Wien] Hartree-Fock and the Hubbard Model
>
>
>Dear WIEN2k community,
>
>From what I understand the Hubbard Model is to calculate the electronic
>repulsion inside the orbitals, specially in the 3d and 4f.
>
>Is it an approximation for the Hartree Fock exchange?
>
>If this is the case then it can be better calculated exact-exchange
>functionals (1, 2)
>
>1) 4.5.7 Onsite-exact-exchange and hybrid functionals for correlated
>electrons
>
>2) 4.5.8 Unscreened and screened hybrid functionals
>
>Cheers
>
>          Pablo de la Mora
>
>
>
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