[Wien] Controversy in band gap values CoSb

[Osama Yassin]

Dear Prof Blaha,,

Thank you for your prompt reply.
Earlier I had used low and dense k-mesh, but it seems I have to rerun scf
with unshifted k-mesh.

Osama

On Fri, Jul 12, 2013 at 10:10 AM, Peter Blaha
<pblaha at theochem.tuwien.ac.at>wrote:

> You missed an important comment:
>
> CoSb3.scf::GAP  :    0.0502 Ry =     0.683 eV   (provided you have a
> proper k-mesh)
>
> PROVIDED YOU HAVE A PROPER K-MESH.
> We discussed this several time in the mailing list. If you do the
> scf-cycle with a shifted k-mesh and the gap is at gamma, the reported gap
> in the scf-file (or the DOS) is NOT ok. (How should it know that the gap at
> gamma is smaller, when gamma is not calculated ??)
>
> You can get a "correct" gap using an unshifted (but denser) k-mesh, or you
> read the gap value from the band structure.
>
>
> Am 12.07.2013 08:54, schrieb wien-bounces at zeus.theochem.**tuwien.ac.at<wien-bounces at zeus.theochem.tuwien.ac.at>
> :
> Dear Prof, Blaha and Wien2k users,,
>
> I'm looking for your urgent help about the following:
>
> - I'm calculating DOS and band structure of CoSb3. I noted strange
> behaviour when comparing the values obtained from DOS and band structure.
> The analysis utility gives me a value of Eg equals to 0.684eV while the
> band structure shows crossing of Fermi level at G-point (i.e metallic). If
> I shifted manually the value of Eg in case.insp to match the top of the
> valence band the band gap appears to be ~ 0.4 eV. These values were
> obtained when I used mBJ scheme. I got similar behaviour when using GGA,
> but of course the Eg values are smaller.
>
> - I have  doubt about something going wrong after preparing the required
> files for the band plot (may be in case.output1). This is because when I
> directly plot bands, i.e without - x lapw1 -band -up/-dn steps, I get the
> correct band gap. Of course the lines look not connected with no symmetry
> points written. However, I'm not sure about what input files I should
> provide to you, I attach case.struct, DOS and the cases of the band plots.
>
>
> Analysis of parameter:
> :FER :GAP
> in CoSb3.scf (showing last 10 / 1 lines)
>
> --- FER -----------
> in  1 files:
> CoSb3.scf::FER  : F E R M I - ENERGY(TETRAH.M.)=   0.5239017718
> --- GAP -----------
> in  1 files:
> CoSb3.scf::GAP  :    0.0502 Ry =     0.683 eV   (provided you have a
> proper k-mesh)
>
>
> I attach two files for plots of DOS and band structures
>
>
> --
> Osama
> Prof Dr Osama Ali Yassin
> Professor of Solid State Physics and ICTP regular associate
> Department of Physics, Faculty of Science
> Taibah University, A-Madinah Al-Munawarh, K. Saudi Arabia
>
>
> --
> Peter Blaha
> Inst.Materials Chemistry
> TU Vienna
> Getreidemarkt 9
> A-1060 Vienna
> Austria
> +43-1-5880115671
> --
> Peter Blaha
> Inst.Materials Chemistry
> TU Vienna
> Getreidemarkt 9
> A-1060 Vienna
> Austria
> +43-1-5880115671
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>



-- 
*Osama          *
*Prof Dr Osama Ali Yassin ** **                     *
*Professor of Solid State Physics and ICTP regular associate*
*Department of Physics, Faculty of Science*
*Taibah University, A-Madinah Al-Munawarh, K. Saudi Arabia *
*
*
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