[Pw_forum] LDA+U calculations to get U and J

[Gianluca Giovannetti]

Dear All,

thank you for the reply. i appreciate it.

i need U and J for a DMFT (homemade) code.
this is the reason i would prefer to calculate U and J via Wannier
formalism.
Wannier functions i have calculated including d and p states/bands in order
to have more localized states and i can have eigenvalues for self-consistent
unperturbed (alpha=0) and perturbed (alpha finite) runs.
i don`t understand if U and J calculated via derivates of eigenvalues
respect occupancies of this two runs are correct.
what is your opinion?

i have the feeling that i should take care to extrapolate for different
sizes of my system in what i`m doing.

What do you mean by  "very similar but another procedure"?

thank you.

Gianluca



On Mon, Feb 15, 2010 at 10:10 AM, Dmitry Korotin <dmitry at korotin.name>wrote:

> Dear Gianluca,
>
> > i would like to calculate the U and J for a given material Fe based.
> > I can do LDA+U calculations without problems is such system using PW.
>
> If you are going to use U and J within original QE code you should
> calculate U and J for atomic states as Matteo Cococcioni suggests.
>
> > In the current distribution of PW in the directory PP there is a file
> > wannier_ham.f90.
> > I believe it is referring to the paper:
> >
> > http://xxx.lanl.gov/pdf/0801.3500
> >
> > The subroutines are reading wfs and eigenvalues of a given
> self-consistent
> > calculation and they calculate the Hamiltonian in Wannier basis set.
> > This gives the possibility to calculate on-site energy of given d states.
> > If now we change the occupancy at a given site by the flag
> Hubbard_alpha()
> > and we recalculate the Hamiltonian in Wannier basis set for such
> > self-consistent calculation, the variation of eigenvalues respect to the
> > occupations should give the U and J parameters.
> > Is this correct?
> > Is this the procedure used in the mentioned paper?
>
> In the mentioned paper was used very similar but another procedure.
> With use of the flag Hubbard_alpha() you are able to change occupancy
> of a pure atomic (pseudoatomic) orbital. If Wannier function differs
> noticeably from pure atomic state standart procedure is not suitable.
>
> --
> Best regards,
> Dmitry Korotin
>
> Ph. D. Student,
> Institute of Metal Physics
> S. Kovalevskaya, 18
> 620041 Ekaterinburg GSP-170
> Russia
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