[Wien] Momentum matrix elements between certain bands along a path

[Yong Woo Kim]

Thank you very much for the reply. It helped me a lot to understand the
data.

As you have suggested I have tried to "count" the eigenvalues in the
case.output1 file but realised that the eigenvalues look strange. The first
86 eigenvalues which I believe have been taken into account in calculating
the momentum matrix are as follows.

     -4.1262932   -4.1256354   -4.1251633   -4.1251633   -4.1249426
     -4.1249426   -4.1248262   -4.1245153   -4.1242407   -4.1242407
     -4.1239953   -4.1239953   -0.9967463   -0.8244089   -0.8036964
     -0.8036964   -0.7806875   -0.7806875   -0.0900531   -0.0168253
      0.0106515    0.0106515    0.0926036    0.1002014    0.1002014
      0.1756061    0.2016896    0.3136943    0.3136943    0.3233102
      0.3233102    0.3821736    0.3821736    0.4154772    0.4154772
      0.4178039    0.8795266    1.0925184    1.2136878    1.2691756

      1.2691756    1.2833408    1.3316029    1.3316029    1.3380241
      1.4260731    1.5008253    1.5008253    1.5092004    1.5092004
      1.5282665    1.5908203    1.5945302    1.7702055    1.7702055
      1.7989177    1.7989177    1.8954264    1.9042000    1.9075892
      1.9230390    1.9230390    1.9674618    1.9674618    2.1821249
      2.1821249    2.1888513    2.1982834    2.1982834    2.2296896
      2.4044660    2.4044660    2.4079853    2.4962868    2.4962868
      2.5909270    2.5909270    2.6344577    2.7437780    2.7437780

      2.7923893    2.7923893    2.9237354    2.9661865    2.9838026
      2.9838026

Looking at the values, I guess the units are in eV.

However, if I actually plot the band structure of Al2O3, there is a large
band gap of about 6 eV and I cannot see this in the data above.

I've tried adding the Fermi energy which seems to be about 5.6 eV but still
it doesn't make sense. The plot of the band structure seems to look okay
comparing with other references. Is there something that I am
misunderstanding about the output file?
The calculation steps that I have carried out (in my memory) are as follows.

init_lapw
run_lapw
create case.klist_band from xcrysden
x kgen
x lapw1
x lapw2 -fermi
x lapw1 -band
x optic

Thank you very much in advance.

Best regards,
Yong Woo Kim
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