[Pw_forum] Fwd: Full LDA+U calculation on orbitals with different orbital angular momentum l

[Suza W]

Dear All,

Yes, WEIN2k allows using U&J for d and f simultaneously.
It would, however, be nice to cross-check the results with Quantum
Espresso.

The articles in literature with other codes are very confusing.

For example,  see PHYSICAL REVIEW B 77, 205202 
2008,
which says (at page 3) :

"By adding Us=43.54 eV, the gap is adjusted to 3.3 eV, close to the
experimental value of 3.4 eV."

I do not understand the underlying philosophy to use such a big U.
Such a crazy value may provide a good band gap but
sometime leads to a crazy phonon frequency
or a crazy magnetic moment value.
Unfortunately, the literature is crowded with such desperate uses of
fitting parameters which confuse a new student too much.  Furthermore,
publishing quick and sloppy articles
can do more harm than good  to good science.
Probably, only an expert can clean the literature by writing an unambiguous
review paper on such desperate attempts.


Has anyone calculated U for ZnO solid self-consistently ?
It is not  so straightforward - it often provides a very big unphysical U,
sometime even a negative value.  I hope to see more tutorials or articles
(transparent) on DFT+U approach on the QE website, in the forthcoming
future.

Best,
Suza

On Fri, Jun 6, 2014 at 8:31 AM, Mehmet Topsakal <mtopsaka at umn.edu> wrote:

> Dear Simone,
>
> WIEN2k allows using U&J for d and f simultaneously.
>
> Bests.
>
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