Dear Pablo,
experts in strongly correlated systems may correct me but my understanding
is that Hubbard U is not a "model" of Hartree Fock exchange. HF is an
approximative treatment of electron-electron interaction, a many body
problem. Hubbard model (where U was originally introduced) tries to
_model_ the same.
In other words, both Hubbard U and DMFT are attempts to capture the effect
of electron correlations which are beyond HF.
Best regards,
Karel
--- x ---
dr. Karel Vyborny
Fyzikalni ustav AV CR, v.v.i.
Cukrovarnicka 10
Praha 6, CZ-16253
tel: +420220318459
On Wed, 16 Nov 2016, delamora wrote:
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-boun...@zeus.theochem.tuwien.ac.at> en nombre de delamora
<delam...@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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Comentarios
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-boun...@zeus.theochem.tuwien.ac.at> en nombre de
t...@theochem.tuwien.ac.at <t...@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 <delam...@unam.mx>
>Reply-To: A Mailing list for WIEN2k users <wien@zeus.theochem.tuwien.ac.at>
>To: A Mailing list for WIEN2k users <wien@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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