[Wien] Hartree-Fock and the Hubbard Model

[Gavin Abo]

Perhaps do a google search for correlated materials.  For example, maybe 
the following references are of interest:

https://en.wikipedia.org/wiki/Strongly_correlated_material#Electronic_structures
https://arxiv.org/abs/1309.3355v1 (Section 1. LDA+U vs Hartree-Fock and 
Exact Exchange)
http://www.cond-mat.de/events/correl12/manuscripts/ (The LDA+U Approach: 
A Simple Hubbard Correction for Correlated Ground States)

On 11/22/2016 3:28 AM, Luis Ogando wrote:
>    Thank you Pablo !
>    I am looking for something introductory like wikipedia. Do you have 
> some reference "in this direction" ?
>    All the best,
>                   Luis
>
>
>
> 2016-11-21 15:25 GMT-02:00 delamora <delamora at unam.mx 
> <mailto:delamora at unam.mx>>:
>
>     Luis, look for Hubbard Model
>
>     NaCl U2
>
>               Pablo
>
>     ------------------------------------------------------------------------
>     *De:* Wien <wien-bounces at zeus.theochem.tuwien.ac.at
>     <mailto:wien-bounces at zeus.theochem.tuwien.ac.at>> en nombre de
>     Luis Ogando <lcodacal at gmail.com <mailto:lcodacal at gmail.com>>
>     *Enviado:* lunes, 21 de noviembre de 2016 11:00:23 a. m.
>     *Para:* A Mailing list for WIEN2k users
>     *Asunto:* Re: [Wien] Hartree-Fock and the Hubbard Model
>     Dear Prof. Tran,
>
>        I would like to read more about this subject, but,
>     unfortunately, your link gave me a message like : " Wikipedia does
>     not have an article with this exact name. "
>        Please*,* could you suggest another non-specialist reference
>     like wikipedia ?
>        Thank you,
>                    Luis
>
>     2016-11-20 13:28 GMT-02:00 <tran at theochem.tuwien.ac.at
>     <mailto:tran at theochem.tuwien.ac.at>>:
>
>         Hi,
>
>         DFT+U is a cheap but rather rough approximation of HF.
>         Beside this, there is also the difference that in DFT+U, the
>         Coulomb
>         operator is attenuated in order to account for the screening
>         due to
>         correlation. In HF, no correlation is included.
>         In hybrids, the screening is included by using only ~25% of HF
>         exchange
>         (and there is also correlation coming from a LDA/GGA
>         correlation term).
>
>         Hybrid, onsite-hybrid and DFT+U are more or less the same,
>         since all of them are one-electron methods and mix HF with
>         LDA/GGA.
>         As Karel said, they are better than LDA/GGA, but can not reproduce
>         the experimental observations that are beyond the one-electron
>         methods.
>         DMFT is better since it is a beyond one-electrons method.
>
>         Read that:
>         https://en.wikipedia.org/wiki/LDA+U
>         <https://en.wikipedia.org/wiki/LDA+U>
>
>         FT
>
>
>             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
>
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