Absorption Coeff.

[Dipankar Saha]

Hi,
Can we directly plot the absorption coeff.  v/s.  energy (eV) ? / Do we need to use the "OpticalSpectrum" object for this purpose... ?

Regards_
Dipankar

[Petr Khomyakov]

To plot absorption coefficient vs energy, one should first calculate it, and this is what OpticalSpectrum analizer essentially does by calculating the imaginary part of the dielectric function related to the absorption coefficient, see http://docs.quantumwise.com/tutorials/optical/optical.html.

[Dipankar Saha]

Thanks a lot for the reply ...

Best_
Dipankar

[Dipankar Saha]

Hi,

Is it possible to obtain the optical spectrum (or, Absorption v/s. Energy)...  with/ with-out electron-hole interactions ??

Best_
Dipankar

[Petr Khomyakov]

To account for two particle excitations in the optical spectrum, one should adopt a many-body approach that goes beyond the ground state density functional approach implemented in ATK.   

[Dipankar Saha]

Okay, I understand...  
..................

 Now, for example the dielectric constant is not isotropic ...i.e.,  e_xx =e_yy , but not equals to e_zz ... then how do you calculate "extinction coefficient" (rather, e₁ and e₂)?

Besides,  while finding absorption coefficient of any wide band S.C. ...how critical is the selection of the parameters e.g. , broadening, bands_below_fermi_level,  and  bands_above_fermi_level ??

Thanks and Regards_
Dipankar
 

[Petr Khomyakov]

One should adopt sufficient number of bands to accurately calculate the absorption coefficient.  The actual numbers depend on the considered system and required accuracy.