[Wien] Optical gap

[Gavin Abo]

Absorption coefficient can be used to make Tauc plot and tangent method 
gives Tauc gap [ https://en.wikipedia.org/wiki/Tauc_plot ].

Optical gap is determined from the plot of epsilon2 (the imaginary part 
of the dielectric function) using the tangent method.

To visualize what Xavier describes in the posts at

https://www.mail-archive.com/wien@zeus.theochem.tuwien.ac.at/msg08951.html

see for example Figure 7 in the article titled "Band Gap Determination 
from Diffuse Reflectance Measurements of Irradiated Lead Borate Glass 
System Doped with TiO2 by Using Diffuse Reflectance Technique" by S. 
Ebraheem and A. El-Saied [ 
http://file.scirp.org/Html/8-7701026_31475.htm ].  This article also 
describes how r might be determined for the Tauc plot.

On 3/7/2016 3:05 PM, said chibani wrote:
> Dear Wien Users ,
> how to determineoptical gapfromthe graph of opticalproperties ? is 
> determine from the graph of absorption coefficient? and how ?
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