[Wien] validity and use of Kramer Kronig transformation

[abdel Mar..]

Dear Wien2k users,

 My question is about the validity of KK trasformation, My goal is to use the program x kram to calculate  refractive index n from  extinction coefficient k.

   I tested it but I can not find the same result. 

1.first I calculate k and n with the "normal" calculation.

#
# Lorentzian broadening with gamma= 0.000000  [eV]
# Im(epsilon) shifted by   0.0000   [eV]
# No intraband contributions added
#
# Energy [eV]  ref_ind_xx    extinct_xx
#
   0.136060  0.751815E+01  0.391540E+00
   0.408170  0.102717E+02  0.181928E+01
   0.680280  0.231108E+01  0.683176E+01
   0.952400  0.307707E+01  0.171773E+01
   1.224510  0.326844E+01  0.132376E+01
   1.496630  0.840948E+01  0.658562E+01
   1.768740  0.323558E+01  0.457868E+01
   2.040850  0.187595E+01  0.432633E+01
   2.312970  0.135153E+01  0.372669E+01
   2.585080  0.105249E+01  0.329286E+01
..........          ..................         ...............
13.197530  0.786248E+00  0.202728E-01


now if i calculated  case.refraction from imposed case.joint ( Enegry vs k calculated from 1) to found n
the result is different from the first calculation, in spite of keeping the same case.inkram.

# Lorentzian broadening with gamma= 0.000000  [eV]
# Im(epsilon) shifted by   0.0000   [eV]
# No intraband contributions added.
#
# Energy [eV]  ref_ind_xx    extinct_xx
#
   0.136060  0.213440E+01  0.917213E-01
   0.680280  0.231028E+01  0.147856E+01
   1.224510  0.264705E+01  0.250044E+00
   1.768740  0.150425E+01  0.152191E+01
   2.312970  0.149987E+01  0.124234E+01
   2.857200  0.135466E+01  0.108498E+01
   3.401420  0.123245E+01  0.962223E+00
   3.945650  0.114376E+01  0.859319E+00
   4.489880  0.107170E+01  0.772398E+00
   5.034110  0.100673E+01  0.693421E+00
   5.578340  0.950350E+00  0.616652E+00
   6.122560  0.901011E+00  0.540848E+00
   6.666790  0.856630E+00  0.465609E+00
   7.211020  0.811606E+00  0.384269E+00
   7.755250  0.772218E+00  0.285813E+00
   8.299480  0.765665E+00  0.167031E+00
   8.843700  0.812414E+00  0.855660E-01
   9.387930  0.850233E+00  0.524445E-01
   9.932160  0.875432E+00  0.366219E-01
  10.476390  0.893232E+00  0.279995E-01
  11.020620  0.906918E+00  0.218597E-01
  11.564840  0.917665E+00  0.178932E-01
  12.109070  0.926022E+00  0.149025E-01
  12.653300  0.932594E+00  0.125510E-01

where this difference comes from?
x kram is adapted for epsilon only? if no, how can i use it to calculate "correct" refractive index from extinction coefficient?
should I use another program to do that , if so, which one, please?

Regards



 		 	   		  
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