[Pw_forum] thin film construction

[Stefano Baroni]

On Sep 16, 2009, at 7:34 PM, dev sharma wrote:

> hi 2 all,
>
> I am somewhat confused about construction of a film. like whenever  
> we calculate the band gap of a unit cell of any system and 2*2*2  
> supercell  of that system we get the same value whereas when one  
> moves from nano regime to larger scale the band gap should decrease.  
> It means that the unit cell is treated as crystal.So, if i construct  
> a film , by taking it as 2*2*1 supercell, it will again consider it  
> as sum of crystals and will yield the same results ?????  Hope so  
> that my question is clear ..

Not to me ...

> How to make a structure of  film ???

using supercells "intercalated" with vacuum, the same way you would to  
simulate a surface. Only, in this case the thickness of the slab is  
not an artifact of the model, but corresponds to the physical  
thickness of the film (if the film is thin enough to be simulated with  
a supercell)

SB

> Thanks in advance.
> With regards,
> Dev Sharma
> _______________________________________________
> Pw_forum mailing list
> Pw_forum at pwscf.org
> http://www.democritos.it/mailman/listinfo/pw_forum

---
Stefano Baroni - SISSA  &  DEMOCRITOS National Simulation Center -  
Trieste
http://stefano.baroni.me [+39] 040 3787 406 (tel) -528 (fax) /  
stefanobaroni (skype)

La morale est une logique de l'action comme la logique est une morale  
de la pensée - Jean Piaget

Please, if possible, don't  send me MS Word or PowerPoint attachments
Why? See:  http://www.gnu.org/philosophy/no-word-attachments.html







-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.quantum-espresso.org/pipermail/users/attachments/20090916/925be666/attachment.html>