[Wien] Hartree-Fock and the Hubbard Model

[Luis Ogando]

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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