[Wien] metal or semiconductor

[Wien2k User]

Dear Prof. Peter BLAHA

Thank you for all these explanations

for our system, the gap is built by 3d-states of Neodymium only

within GGA+U,  Fermi level passes through the top of the valence band with
the presence of a band overlap between 3d states. But by adding mBJ, the
level shifts to the top of the valence band with a creation of a band-gap

We have considered thta mBJ is more suitable for our system, but we are
still waiting for comments from you

Thanks again



Le mer. 7 août 2019 à 20:38, Peter Blaha <pblaha at theochem.tuwien.ac.at> a
écrit :

> GGA+U affects only the position of the correlated electrons (3d band or
> 4f, ..), but not of the delocalized states (eg. Ni-4s band in NiO)
>
> Therefore you cannot get the correct gap in NiO with GGA+U, because the
> Ni-4s states limit the size of the gap, even when you split the d-band
> by an enormous U.
>
> mBJ also affects the Ni-4s states and shift it up, so that the gap is
> correct.
>
> On the other hand, for 4f systems, mBJ can be too "weak" to open a gap.
>
> Since we do not know your compound, we cannot say anything concrete,
> but: yes, there is a possibility that GGA+U still gives a metal while
> mBJ gives a semiconductor.
>
>
>
> Am 07.08.2019 um 19:39 schrieb Wien2k User:
> > Dear Prof.Laurence Marks
> > thank you very much for your reply
> >
> > my scientific reasoning is the following;
> > i noticed that mbj and GGA+U give almost the same band topology except
> > that mBJ caused a band shift that showed semiconductor behavior,
> > i think that mBJ is better suited to describe band-gaps than GGA+U, i
> > think the material is semiconductor
> >
> > I still have a confirmation or another explanation
> >
> > Le mer. 7 août 2019 à 19:30, Laurence Marks <laurence.marks at gmail.com
> > <mailto:laurence.marks at gmail.com>> a écrit :
> >
> >     A good question which nobody can answer for you. These questions are
> >     why we do science.
> >
> >     _____
> >     Professor Laurence Marks
> >     "Research is to see what everybody else has seen, and to think what
> >     nobody else has thought", Albert Szent-Gyorgi
> >     www.numis.northwestern.edu <http://www.numis.northwestern.edu>
> >
> >     On Wed, Aug 7, 2019, 18:22 Wien2k User <wien2k.user at gmail.com
> >     <mailto:wien2k.user at gmail.com>> wrote:
> >
> >         Dear Wien2k users;
> >
> >
> >         after GGA+U+SOC calculation,  I found that the studied material
> >         is a metal ( even for a large value of Ueff ) but when I redid
> >         another calculation with mBJ based on GGA+U+SOC
> >         {mbj(GGA+U+SOC)}, I found a semiconductor.
> >
> >         Which of these two behaviors is the most correct?
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>
> --
> --------------------------------------------------------------------------
> Peter BLAHA, Inst.f. Materials Chemistry, TU Vienna, A-1060 Vienna
> Phone: +43-1-58801-165300             FAX: +43-1-58801-165982
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