[Wien] absorption coefficient

[Pavel Ondračka]

fatima DFT píše v Čt 03. 08. 2017 v 15:50 +0530:
> Dear Users of Wien2k
> 
> I want to simulate optical properties of a perovskite compound.
> In the literature people have reported a sharp peak at 1.6 eV while I
> am not getting it.
> Here is the file from literature and here is the file that I got from
> Wien2k.
> Does including -SO in the calculation may effect the shape of the
> absorption curve?
> 
> 
> Regards
> Fatima
> 
Dear Fatima,

it is hard to tell without the knowledge of the compound, however in
general sharp peaks like this near the absorption edge are usually
caused by excitonic effects, which are not included in the optic
package (it uses just random phase approximation without local field
effects). If you compound is not too complicated and you are skilled
enough, you can try the BSE unsupported package which can calculate the
optical spectra including the excitons to see it helps. Just be warned,
it is unsupported and much less documented than the Wien2k standards.
Moreover, to get even somewhat converged results requires a LOT of CPU
time and a LOT of memory.

Best regards
Pavel