[Wien] Hartree-Fock and the Hubbard Model

[Luis Ogando]

   Hi Gavin,

   Thank you very much ! I will take a look !
   All the best,
                   Luis


2016-11-22 9:50 GMT-02:00 Gavin Abo <gsabo at crimson.ua.edu>:

> 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>:
>
>> Luis, look for Hubbard Model
>>
>> NaCl U2
>>
>>           Pablo
>> ------------------------------
>> *De:* Wien <wien-bounces at zeus.theochem.tuwien.ac.at> en nombre de Luis
>> Ogando <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>:
>>
>>> 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
>>>
>>> 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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