[Wien] Question concerning dielectric tensor

[Peter Blaha]

Please rerun   x lapw2 -fermi with the TETRA option, but eval eq. 101.
to switch off the non-linear "Bloechl-corections", which can cause negative
weights and thus negative epsilons. (seach UG for "optics" and see all
related comments)

Please note, this is necessary only for metals!


Am 26.07.2011 18:12, schrieb Sebastian Putz:
> Dear WIEN2k users,
>
>
> I have a question concerning the calculation of the dielectric tensor.
>
>
> I used the standard procedure to obtain the components of the dielectric tensor for an optically anisotropic slab (converged density -> optic -> joint -> kram). However, in the
> kram output file "case.epsilonup" I obtain negative values (see below) for some of the tensor components at some energies. I found that the user guide states on page 151:
> "Warning: Negative values for epsilon_2 may occur due to negative weights in Blöchl's tetrahedron method". What does this actually mean? Are these values useless/unphysical then?
>
>
> As I would like to postprocess the data for the dielectric tensor I need to know how to deal with these negative values. Is it sufficient just to take the absolute value? If not,
> how can I interpret these negative values for some tensor components?
>
>
> Below you see a part of the "case.epsilonup" file showing the negative values:
>
>
> ===== case.epsilonup ==========================================================================
>
> #
>
> # Lorentzian broadening with gamma= 0.100000 [eV]
>
> # Im(epsilon) shifted by 0.0000 [eV]
>
> # No intraband contributions added
>
> #
>
> # Energy [eV] Re_eps_xx Im_eps_xx Re_eps_yy Im_eps_yy Re_eps_xy Im_eps_xy
>
> #
>
> 0.013610 0.355073E+03 0.267270E+03 0.379411E+03 0.284541E+03 -0.433910E+01 -0.111993E+01
>
> 0.040820 0.320451E+03 0.295130E+03 0.341538E+03 0.316236E+03 -0.432648E+01 -0.321273E+01
>
> 0.068030 0.268282E+03 0.302792E+03 0.284004E+03 0.326426E+03 -0.343964E+01 -0.472158E+01
>
> 0.095240 0.216111E+03 0.294926E+03 0.225588E+03 0.319308E+03 -0.210235E+01 -0.530955E+01
>
> 0.122450 0.171960E+03 0.280008E+03 0.175154E+03 0.303207E+03 -0.899641E+00 -0.512592E+01
>
> 0.149660 0.135931E+03 0.264191E+03 0.133648E+03 0.284249E+03 -0.871710E-01 -0.458024E+01
>
> 0.176870 0.105154E+03 0.249611E+03 0.991686E+02 0.264968E+03 0.386425E+00 -0.398342E+01
>
> 0.204090 0.772605E+02 0.235509E+03 0.700520E+02 0.245693E+03 0.658656E+00 -0.345529E+01
>
> 0.231300 0.517615E+02 0.220269E+03 0.455810E+02 0.226285E+03 0.825314E+00 -0.300510E+01
>
> 0.258510 0.295843E+02 0.203095E+03 0.254419E+02 0.206806E+03 0.930218E+00 -0.261269E+01
>
> 0.285720 0.117812E+02 0.184586E+03 0.942771E+01 0.187538E+03 0.985082E+00 -0.226081E+01
>
> 0.312930 -0.144786E+01 0.166031E+03 -0.269328E+01 0.168949E+03 0.988609E+00 -0.195118E+01
>
> 0.340140 -0.107062E+02 0.148526E+03 -0.113783E+02 0.151602E+03 0.953669E+00 -0.169726E+01
>
> 0.367350 -0.168993E+02 0.132631E+03 -0.173011E+02 0.135876E+03 0.903225E+00 -0.149950E+01
>
> 0.394570 -0.208346E+02 0.118478E+03 -0.211441E+02 0.121895E+03 0.853612E+00 -0.134912E+01
>
> 0.421780 -0.231246E+02 0.106034E+03 -0.234971E+02 0.109621E+03 0.817793E+00 -0.123489E+01
>
> ===============================================================================================
>
>
> Any help would be greatly appreciated.
>
>
> Best regards,
>
> Sebastian Putz
>
>
> ================================
> Dipl.-Phys. Sebastian Putz
> Institute of Theoretical Physics (Group Prof. Fabian)
> University of Regensburg
> Universitätsstraße 31
> 93040 Regensburg, Germany
> Tel.: 0941 943 2032
> E-mail: sebastian.putz at physik.uni-regensburg.de
>
>
>
>
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-- 

                                       P.Blaha
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Peter BLAHA, Inst.f. Materials Chemistry, TU Vienna, A-1060 Vienna
Phone: +43-1-58801-15671             FAX: +43-1-58801-15698
Email: blaha at theochem.tuwien.ac.at    WWW: http://info.tuwien.ac.at/theochem/
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