[Wien] Gap calculated with GGA+U, mBJ and HF

[Wien2k User]

thank you for your answers

But for my problem is what I have to say that the material is semimetalic
since this result is obtained with GW, GGA+U and mBJ?.
Or I have to present all the results even those obtained by HF and I would
say that the calculations gave different results pending confirmation of
the experiment?


2017-08-07 8:38 GMT+02:00 Víctor Luaña Cabal <victor at fluor.quimica.uniovi.es
>:

> On Mon, Aug 07, 2017 at 01:32:04AM +0200, Wien2k User wrote:
> > I calculated the gap of a material whose experimental value is unknown.
> >
> > With GGA+U, mBJ potential and GW, I found that this material is semimetal
> > (a slight band overlap) but with HF i found it to be semiconductor of
> very
> > small gap.
> >
> > How can I know what is the real nature of the gap of this material?
> >
> > This calculation is a part of a future paper so I have to put all found
> >  results (GGA + U, mBJ, GW and HF) in spite of what give deferent nature
> or
> > I have to adopt that of the HF since it is a more accurate method?
>
> This is a very good question related to the nature and philosophy of
> theoretical calculations.
>
> Assuming that the role of a theoretical calculation is predicting or
> duplicating the experimental results is a dead way when the theory is yet
> imprecise or incompletely developed.
>
> In fact, as theory matures it becomes a part of engineering and it
> can be accepted that doing a calculation can sustitute performing an
> experiment. When designing a building or a bridge. Nobody would accept
> that a good resistence analysis is missed, but that means that materials
> resistence is well known in advance.
>
> Until theory reaches that point of development, the role of a good
> calculation is determining how dependent are the obtained properties
> to the inner parameters of the calculation. So, in your example,
> I would give more value to exploring the effects and meaning of the
> different methods.
>
> Also the examination of families of compounds in looking for the most
> promising candidates can be of great help, even in early stages of
> a research.
>
> Hope this helps,
>                 Víctor Luaña
> --
>     .  .    "Half of the US people use twitter to form its opinion and half
>    / `' \   also elect the US president. I only hope they are not the same
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> ==(((==)))===================================+===========================
> ! Dr.Víctor Luaña, in silico chemist & prof. !
> ! Departamento de Química Física y Analítica !
> ! Universidad de Oviedo, 33006-Oviedo, Spain !
> ! e-mail:  <victor at fluor.quimica.uniovi.es>  !
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