[Wien] How to calculate Plasma Frequency and Number of effective electrons.

[Kulpreet Virdi]

Hi Zaid, 

yes, one way of identifying the Plasmon (energy) is the
maximum in loss function (electron energy loss plot) however this is not
always correct. The loss function is given by Im [-1/ε] which is equal to
[ε2/(ε1^2+ε2^2)]. In the loss function you would see a maximum when there
is a local minimum of (ε1^2+ε2^2) or a local maximum of ε2. 

The local
maxima of ε2 imply interband transition(s) ; which are often visible in
loss spectrum especially for materials containing transition or heavy
metals. However a minima of (ε1^2+ε2^2) implies a plasmon excitation. 

The
most often used definition of plasmon is when ε2 crosses zero [and a minmum
of ε1^2+ε2^2 ] with a positive slope with respect to the energy axis. For
details you can check either of these 

M. Fox, Optical Properties of
Solids (Oxford University Press,
Oxford, UK, 2010). 

V. Gallegos-Orozco,
R. Martınez-Sanchez, and F. Espinosa-
Magana, Phys. Rev. B 77, 045128
(2008). 

V. J. Keast, A. J. Scott, M. J. Kappers, C. T. Foxon, and C.
J.
Humphreys, Phys. Rev. B 66, 125319 (2002). 

I guess someone else could
help you with the effective number of electrons. 

All the best, 

Kulpreet


On Fri, 12 Apr 2013 12:30:09 +0800, Zaid  wrote:     Respected Wien
Users

 I am inexperience in calculating optical properties May any one
guide me how to calculate Plasmon energy and Number of effective electrons
? After some effort I came to know that the energy associated to highest
peak value in Electron loss plot will be Plasmon energy. While value for No
of effective electrons can be obtained from X KRAM sumrule. Can Any one
confirm this information true ? And which sum rule should be selected ? 


Best Regards M, Zaid   

 
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