[Wien] metal or semiconductor
Peter Blaha
pblaha at theochem.tuwien.ac.at
Thu Aug 8 07:22:07 CEST 2019
Nd does not have 3d valence states.
Am 07.08.2019 um 22:35 schrieb 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 acreationof 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
> <mailto: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>
> > <mailto: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>
> <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>
> > <mailto: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
> Email: blaha at theochem.tuwien.ac.at
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Peter BLAHA, Inst.f. Materials Chemistry, TU Vienna, A-1060 Vienna
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Email: blaha at theochem.tuwien.ac.at WIEN2k: http://www.wien2k.at
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