[Pw_forum] band structure

[Stefano Baroni]

Tha facts are right, the explanation is missing (or not clearly stated)
The fact is, the SC Gamma pooint (or any other k vector, for that  
matter) contains four times as many electron states as the FCC Gamma  
point (have you noticed this?). This is because the BZ is four times  
as small, and the total number of k point in the BZ cannot depend on  
one's ability to identify the proper crystal symmetries.

Can you see which FCC k points are *folded* into the SC gamma point?

SB

On Jun 10, 2008, at 7:21 AM, 程迎春 wrote:

>
>
> What happens if you consider the crystal as SC, rather than FCC?
>
> The gap is direct when the crystal is considered as SC. The bottom  
> of conduction band and the top of valence band are both at Gamma.
> The first Brillouin zone of the FCC is larger than that of the SC.  
> The reduction of the brillouin zone of the SC crystal may induce the  
> K point near X in FCC  superpose with Gamma in SC, so the gap of SC  
> is  direct .
> Am I right?
>
>
> -- 
> Y. C. Cheng
> Department of Phyics
> Nanjing University
> Nanjing 210093
> P. R. China
> Tel: 86-25-83592907
> Email: yccheng.nju at gmail.com  
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---
Stefano Baroni - SISSA  &  DEMOCRITOS National Simulation Center -  
Trieste
http://www.sissa.it/~baroni / [+39] 040 3787 406 (tel) -528 (fax) /  
stefanobaroni (skype)

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