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
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
:
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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