[Pw_forum] Hubbard U

[Matteo Cococcioni]

Dear Tommaso,

see below.

On Fri, May 16, 2014 at 10:40 AM, Tommaso Francese <
neutrinofrancese at gmail.com> wrote:

> Dear all,
>  as you suggested, i try to follow your tutorial for the Hubbard U
> coefficients determination, but i have some practical difficulties.
>
> Summarizing, i proceded as follow:
>
> step 1)—> i have done a simple SCF with very low coefficients for
> Hubbard_U1 and Hubbard_U2, enabling the wavefunction separate collection
> (wf_collect) ;
>

I don't think wf_collect is necessary. should not be harmful either


> step 2)—> i have performed some SCF, restarting from the charge file
> stored previously,  introducing some fluctuation values in Hubbard_alpha
> (?), is it correct?
>
>
right.


> the problem is at this point: do i need to rename every scf-file in which
> i performed a different perturbation?



yes, otherwise you overwrite them each time. or you can redirect them to
different (properly named) directories.



> How can i, in the next step, “recall” the different perturbation that i
> performed previously?
>
>
what do you exactly mean by "recall"? do you have difficulties in
recognizing outputs corresponding to different alphas? then see the naming
problem at the previous point.


> At this point is obvious that i don’t know also how to calculate the
> response functions and so, obtaining the Hubbard U coefficient.
>
>
this is what the tutorial is for. were you able to follow the instructions
to the end? Besides the one from the Santa Barbar school there is also
another one from a nother school in 2012 at Penn State. Maybe that is
better?

best,

Matteo




> Can someone help me?
> Thanks a lot,
> Tommaso,
> Università Cà Foscari of Venice
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