[Pw_forum] calculation of absorption spectrum

[Muhammad Adnan Saqlain]

Dear Federico

Thanks for your detailed response. I would look meet prof. Seymour 
Cahangirov. I actually, have recently joined Bilkent, so do no know many 
people yet.


On 09/17/2016 04:41 PM, Federico Iori wrote:
> Hi.
>
> In my opinion, I think the approach you chose depends strictly from 
> the question you want to answer and after that from the the size 
> (number electrons, Number plane wave thou) you have.
> Do you need a full excitonic optical spectrum ? or just a RPA spectrum 
> is sufficient for your study?
>
> If it is silicon-like and then maybe not too much computationally 
> demanding, I think you can use a linear response TDDFT as a first step 
> and then move to a more sophisticated approach as GW (to calculate not 
> the optic, but the screening of your material) + Bethe-Salpeter 
> equation BSE to have correctly acces to the excitonic effects in your 
> absorption spectra.
>
> Of course all the calculations have to be converged wrt kpoints, 
> number of Gvectors, number of bands. When increasing these parameters 
> wrt their pristine value for your converged density in the DFT 
> framework the computational cost will increase not linearly.
>
> I would suggest you to have a look and to do the tutorial with the  
> Yambo code on a small system as they proposed in order to correctly 
> understand what are you doing.
>
> Moreover there is the theory to have a look at in order to understand 
> the meaning and the effect of the quantities you are calculating .
> I would reccomend especially
> Onida Reining Rubio Rev Mod Phys 2002 
> http://journals.aps.org/rmp/abstract/10.1103/RevModPhys.74.601
> as all the others references in the yambo website as well.
>
> Moreover, since I notice you are in Bilkent UNiv, try to ask  to 
> Seymour Cahangirov from the same univ. I think he can address you 
> properly.
>
> I hope this could help a bit.
>
> With the best
> Federico
>
>
>
> Université Paris-Sud 	
> *Federico IORI*
> Marie Curie Fellow
> Laboratoire de Physique des Solides
> Bâtiment 510 - Rue André Rivière
> 91400 Orsay
>
>
>
> ------------------------------------------------------------------------
> *De: *"Muhammad Adnan Saqlain" <saqlain at bilkent.edu.tr>
> *Para: *"pw forum" <pw_forum at pwscf.org>
> *Enviados: *Sábado, 17 de Septiembre 2016 13:25:12
> *Asunto: *[Pw_forum] calculation of absorption spectrum
>
> Dear users
>
> I have a system consisting of 94 atoms (periodic with cell lengths of
> 16.5, 8.5 and 8.7). I want to calculate its absorption spectrum. Can
> anyone guide me which technique would be easy to run. Actually, we have
> 16 core machine and we can run a job for a maximum of 15 days only.
> Based upon this time limit, I would like to know which technique would
> be suitable. TDDFT or GW?
>
> any help in this regards would be highly appreciated.
>
> Thanks
>
> Adnan
>
> Bilknet U. Ankara
>
> _______________________________________________
> Pw_forum mailing list
> Pw_forum at pwscf.org
> http://pwscf.org/mailman/listinfo/pw_forum
>
>
>
> _______________________________________________
> Pw_forum mailing list
> Pw_forum at pwscf.org
> http://pwscf.org/mailman/listinfo/pw_forum

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.quantum-espresso.org/pipermail/users/attachments/20160918/37c0c263/attachment.html>