[Wien] Ueff

[karima Physique]

Dear Dr. Martin Pieper
Thank you very much for your reply.

2017-11-28 14:02 GMT+01:00 pieper <pieper at ifp.tuwien.ac.at>:

>
> Until one of the real experts (I am not among them) finds time to answer:
> My guess is that both is correct, Ueff=U-J as well as Ueff=U-J/2. That is,
> the meaningful thing to do is set J=0 (see UG section on ORB), and not
> estimate it from DFT.
>
> The common ground between ORB or DFT and the magnetism of atoms as in
> Hunds rules is a multiband Hubbard model.
>
> For the latter, the multiple correlation energy parameters of such a model
> are summarized into one intra-orbital U, one inter-orbital V, and a Hund's
> rule parameter J reducing the inter-orbital correlation energy for same
> spin direction. [1].
>
> For the former, the parameter Ueff represents on-site contributions to the
> correlation energy which are underestimated by L(S)DA. Ueff is, therefore,
> an approximation that has to estimate the contribution already accounted
> for by L(S)DA  - which leads to options 1,2,3 for different
> self-interaction corrections.
>
> I doubt that there is a general and safe way to assign specific parts of
> the correlation energy to U, V, and J. At least, the authors of the ORB
> code recommend to avoid the ambiguities [2], and to set J=0.
>
> [1] see for example, the talk 'Localized Electrons with Wien2k' by Elias
> Assmann Wien, workshop 2013, ldau.pdf among the documentations on the
> Wien2k site
> [2] G. K. H. Madsen and P. Novák, Europhys. Lett. 69, 777 (2005)
>
> ---
> Dr. Martin Pieper
> Karl-Franzens University
> Institute of Physics
> Universitätsplatz 5
> <https://maps.google.com/?q=Universit%C3%A4tsplatz+5&entry=gmail&source=g>
> A-8010 Graz
> Austria
> Tel.: +43-(0)316-380-8564
>
>
>
> Am 28.11.2017 08:42, schrieb karima Physique:
>
>> Dear prof. P. Blaha and wien2k users :
>>
>> I am still waiting for your answers and I thank you in advance.
>>
>> my question was :
>>
>> Does Ueff=U-J or Ueff=U- 1/2 J? how to estimate J using constrained
>> DFT.?
>>
>> Thank you in advance
>>
>> 2017-11-27 12:05 GMT+01:00 karima Physique
>> <physique.karima at gmail.com>:
>>
>> Dear Wien2k users:
>>>
>>> Does Ueff=U-J or Ueff=U- 1/2 J? how to estimate J using constrained
>>> DFT.?
>>>
>>> Thank you in advance
>>>
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