[Wien] Optical Properties

[Peter Blaha]

a) Do  ot change the defaults in the inop and injoint files for k-points and band indices.
They are by default ok, and it is only used for special analysis.

b) You cannot get optic with just 1 k-point. joint uses the tetrahedron method and in this case
all vertices have identical energies, so you only get a series of delta-functions, but they will
not fall on your energy-grid and thus you get only zeros.

Even for a large cell you need an extended k-mesh for optics (non-scf)

Am 08.03.2013 05:31, schrieb Choudhary,Kamal:
> Hi
>
> I am trying to reproduce the optical properties of ytrium alumunium garnet as published in Xu, Y.N., Chen, Y., et al., Phys. Rev. B 65, 235105 (2002) with WIEN2k. After
> doing a gamma point calculation for 160 atoms, I got nice density of states, but my optical properties doesn't seem to be good. I used the following input files:
> 1) case.inop
> 1 1 number of k-points, first k-point
> -5.0 2.0 energy window for matrix elements
> 1 number of cases (see choices)
> 1 Re <x><x>
> OFF write unsymmetrized matrix elements to file?
>
> 2) case.injoint
>   1  1504 1504              : LOWER,UPPER and (optional) UPPER-VAL BANDINDEX
>     0.0000    0.00100   1.0000 : EMIN DE EMAX FOR ENERGYGRID IN ryd
> eV                            : output units  eV / ryd  / cm-1
>       6                        : SWITCH
>       2                        : NUMBER OF COLUMNS
>     0.1  0.1  0.3              : BROADENING (FOR DRUDE MODEL - switch 6,7 -
> ONLY)
>
>
> 3)case.inkram
>   0.1    Gamma: broadening of interband spectrum
>    0.0    energy shift (scissors operator)
>    0      add intraband contributions? yes/no: 1/0
>   0.0   plasma frequencies  (from joint, opt 6)
>    0.20   Gammas for Drude terms
>
> But, in the outputjoin files and epsilon files I am getting Re(eps) 1 and Im(eps) zero, which shouldn't be:
> ==================================================
>   Plasma frequencies:
>
>         w_p_xx    [eV]
>
>         0.0000
> #  Energy  [eV]   Im(eps)xx      Re(eps)xx
>
>       0.013606   0.000000E+00   0.100000E+01
>       0.027211   0.000000E+00   0.100000E+01
>       0.040817   0.000000E+00   0.100000E+01
>       0.054423   0.000000E+00   0.100000E+01
>       0.068028   0.000000E+00   0.100000E+01
>       0.081634   0.000000E+00   0.100000E+01
>       0.095240   0.000000E+00   0.100000E+01
>       0.108846   0.000000E+00   0.100000E+01
>       0.122451   0.000000E+00   0.100000E+01
>       0.136057   0.000000E+00   0.100000E+01
>       0.149663   0.000000E+00   0.100000E+01
> ============================================
>
> I tried  both swith 4 and 6 in injoint files leading to same result.
> Could anyone please tell me where am I doing mistake?
>
> Best Regards
> Kamal Choudhary
>
>
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-- 
-----------------------------------------
Peter Blaha
Inst. Materials Chemistry, TU Vienna
Getreidemarkt 9, A-1060 Vienna, Austria
Tel: +43-1-5880115671
Fax: +43-1-5880115698
email: pblaha at theochem.tuwien.ac.at
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