[Wien] Question concerning dielectric tensor

[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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