[Wien] metal supercell band folding dielectric function

[Peter Blaha]

a) Do an optics calculation for the same 32 atom Au-supercell, but without dopant,
just "label" one Au atom by "Au1", so that the symmetry is identical to your Cd-doped
calculation. This should give identical eps2 than the small Au calculation (beware of
k-mesh effects !!!)
b) Use bandstructure with "fat-bands" and partial DOS for analysis of your doped system.
    You can also run optics with matrix-elements restricted to eg. only Cd or only Au
    (missing crossterms). See UG for details.

Am 30.03.2013 00:27, schrieb MingWenmei:
> Dear all,
>
> I am calculating the interband dielectric function of Au with low concentration of Cd dopant (say 1/32 atom concentration). Very strikingly in low energy (< 1eV) range,
> there appears a high peak (~a few hundred). However for FCC pure gold, the interband dielectric function is very small (around zero) below 1eV.
>
> So my question is physically why the dielectric function changes this dramatically? I did the band structure calculation. I found within small energy range (<1eV) of Fermi
> energy for the doped system, there are some extra bands. I began to realize it is this small energy difference of the bands above Fermi energy that causes the high peak of
> dielectric function.
>
> These extra bands may be from doped Cd and also may be from the band-folding of host Au in the supercell calculation. The contribution from supercell itself to the
> dielectric peak seems not to make sense physically. For if band-folding can affect the value of dielectric function, then even for pure FCC Au we may get significantly
> different dielectric functions by choosing "unit cell" of different size (say 1x1x1, 4x4x4 times primary cell )
>
> Could anyone give some comment to understand this?
>
> Thank you a lot,
>
> Wenmei
>
>
>
>
>
>
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-- 
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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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