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

[Gianluca Giovannetti]

Dear Matteo,

i had a look to the NiO example at the link:

http://www.quantum-espresso.org/wiki/images/f/f4/Handson_ldau.pdf

There, one can find the possibility to look at magnetic system with the flag
"magn" in the file resp_mat.in.

However resp_mat.f90 has not such variable in the file.
do i think it wrong?

thank you.

Gianluca

On Tue, Feb 16, 2010 at 8:13 PM, Matteo Cococcioni <matteo at umn.edu> wrote:

> Gianluca Giovannetti wrote:
> > Dear Matteo,
> >
> > thank you for the link.
> > now it is fine.
> > i can calculate U with your scheme. :-)
> >
> > what about J ?
> >
>
> Dear Gianluca
>
> the formal extension of the linear-response machinery to compute U to a
> spin-resolved case (using magnetization instead of
> occupations) doesn't work to obtain J.
> this is at least my experience.
>
> regards,
>
> Matteo
> > cheers,
> >
> > Gianluca
> >
> > On Mon, Feb 15, 2010 at 2:45 AM, Matteo Cococcioni <matteo at umn.edu
> > <mailto:matteo at umn.edu>> wrote:
> >
> >
> >     Dear Gianluca,
> >
> >     here is the link to a tutorial on how to compute the U:
> >
> >     http://media.quantum-espresso.org/santa_barbara_2009_07/index.php
> >
> >     This method uses the atomic occupations defined as in the PRB '05
> >     paper
> >     you refer to in your email.
> >
> >     For sure one could use Wannier functions ainstead of atomic orbitals.
> >     HoweverI have no direct experience with that
> >     so I cannot tell you how to do this in practice.
> >
> >     regards,
> >
> >     Matteo
> >
> >     Gianluca Giovannetti wrote:
> >
> >     > Dear All,
> >     >
> >     > 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.
> >     >
> >     > The paper "Phys. Rev. B 71, 035105 (2005)" well explains how to
> >     > calculate the parameter U.
> >     > i have however troubles in setting the input files to do the
> >     calculations.
> >     > could some examples be provided?
> >     >
> >     > I have also another question.
> >     >
> >     > 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?
> >     >
> >     > thank you.
> >     >
> >     > cheers,
> >     >
> >     > Gianluca
> >     >
> >     >
> >
> ------------------------------------------------------------------------
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> >
> >
> >     --
> >     %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
> >     Matteo Cococcioni
> >     Department of Chemical Engineering and Materials Science,
> >     University of Minnesota
> >     421 Washington Av. SE
> >     Minneapolis, MN 55455
> >     Tel. +1 612 624 9056    Fax +1 612 626 7246
> >     %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
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