[Wien] Band gap

[Gerardo Felix Martinez]

HI dear wien users. I found the following method in the mailing list to
calculate the band gap from the case.scf file. My question is: is there a
way to know if the band gap is direct or indirect using this method? and
what if the conductance band maximum - valence band minimum rest is
negative??

Thanks a lot.

          Bandranges (emin - emax):
:*BAND   :   2   -1.342369   -1.287164
*:*BAND   :   3   -1.319547   -1.287164
*:*BAND   :   4   -1.300594   -1.287164
*:*BAND   :   5   -0.713233   -0.585214
*:*BAND   :   6   -0.585964   -0.516677
*:*BAND   :   7    0.162252    0.291982
*:*BAND   :   8    0.217723    0.372030
*:*BAND   :   9    0.217723    0.416856
*:*BAND   :  10    0.384882    0.565678
*:*BAND   :  11    0.438274    0.567882
*:*BAND   :  12    0.483644    0.605570
*:*BAND   :  13    0.844622    0.918123
*:*BAND   :  14    0.844622    0.948978
*:*BAND   :  15    1.037366    1.180795
*:*BAND   :  16    1.086124    1.299682
*:*BAND   :  17    1.142834    1.299682
*...

:*FER  : F E R M I - ENERGY(TETRAH.M.)=   0.60557
*
using the Fermi energy level at the a few lines later
:*FER  : F E R M I - ENERGY(TETRAH.M.)=   0.60557
*
One can see immediately the valence band minimum (VBM)  being 0.605570
Ry and conductance band maximum (CBM)  being  0.844622  Ry.
So that the band gap being  0.845- 0.606  = 0.239 Ry = 3.25 eV


I hope this helps.

   Hong
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