[Pw_forum] Computing Second order response

[loc duong ding]

I don't understand why Raman activity in this case is zero. In practical, metallic system also provide Raman peak (ex. Carbon nannotube).  I try to calculate graphene (no gap) and I get the proper result. Can you give some more explanation or suggest me some reference about this topic?

 I appreciate to your instructions.  

>So, the the Raman activity should be 
> zero ...
>SB

On Jun 15, 2010, at 3:50 AM, loc duong ding 
> wrote:

> I calculate zigag nano ribbon with hydrogen terminated at the 
> edge. I checked DOS that showed no gap. 
> 
>> yes - SB
> 
> 
> On Jun 14, 2010, at 
>>> 11:03 AM, loc duong ding 
> wrote:
> 
>>> what's the gap of the 
>> unperturbed 
> 
>>> system?
>>> SB
>> 
>> Actually, 
> this 
>> is the firs time I calculate the Raman spectrum. I don't clear 
> about the gap of 
>> the unperturbed system? It means the electronic 
> band gap?


 -----------------------------------------------
Loc Duong Dinh
Ms-Ph.D Student
Sungkyunkwan Advanced Institute of Nanotechnology,
Sungkyunkwan University,
Suwon, 440-746, Korea 
Email: mambom1902 at yahoo.com, ddloc at skku.edu