[Wien] case.inkram

[Karel Vyborny]

There seems to be one aspect missing in the answers so far: the effect of 
disorder. The width of the Drude peak is basically inversely proportional 
to carrier lifetime and this, in turn, depends on how close is the system 
in question to a perfect crystal.
  While the typical values 0.1 eV (for metals) and 0.05 eV (semiconductors) 
on p. 20 of "instructions of the exercises"

http://susi.theochem.tuwien.ac.at/events/ws2017/notes/Laskowski_optic-xas.pdf

may often be a reasonable guess, the actual lifetimes in a specific sample 
depend on its quality (is it a monocrystal? are there many defects? at 
what temperature? etc.)  There is no "universal" value for low temperature 
carrier lifetime in a given material - a sample of the same metal can have 
Gamma of several 10's of meV and conceivably many 100's of meV may not be 
enough in a different sample.
  The bottomline: in the context of the intraband part of optical spectra 
for a given material, the plasma frequency is "a universal material 
parameter" (it can be evaluated for a perfect crystal) while the Gamma 
parameter is sample-dependent and is best adjusted to a specific 
experimental data.

Best regards,

KV


--- x ---
dr. Karel Vyborny
Fyzikalni ustav AV CR, v.v.i.
Cukrovarnicka 10
Praha 6, CZ-16253
tel: +420220318459


On Sat, 16 Jan 2021, Peter Blaha wrote:

> Please read the instructions of the exercises (optics of Al) of our last 
> workshop at www.wien2k.at.
>
>
> Am 16.01.2021 um 02:26 schrieb karima Physique:
>> Dear WIEN2k users,
>> for intraband contribution, where can I  find the value of Gamma for 
>> Drude term
>> 
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