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

[Matteo Cococcioni]

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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