[Pw_forum] Confusion about band structure

[Giuseppe Mattioli]

Dear Muhammed

> In this case BZ is simple cubic not
> FCC. Now my question is that
> is band gap will be same in both cases for ibrav = 2 and ibrav =1 as
> structure is same i.e
> zinc blende. But band structure is different. {because BZ is different for
> different ibarv}

It seems that you've answered yourself the question...:-)

A further note on the band gap. As ZnO is generally found as wurtzite, rather than zincblende, I do 
not know if the zincblende polymorph has a direct band gap at gamma, like the wurtzite one, or not. 
In the former case, you should find the same gap in fcc and sc structures, as long as the gamma point 
is included in the k-point mesh of both calculations. In the latter case, the conduction band 
minimum may be found at different k-points in the fcc and sc BZ, depending on the folding of the sc 
BZ into the FCC BZ.

HTH

Giuseppe


On Wednesday 27 February 2013 11:06:21 zafar rasheed wrote:
> Dear All
> 
> I am working on ZnO in zinc blende
> phase. I want to calculate band structure of this material. For zinc
> blende  we use ibrav = 2 and Zn ( 0.0 0.0 0.0 ) and O at 0.25 0.25
> 0.25 .
> The Brilliouin Zone is FCC. But if we
> use ibrav = 1 (which is for simple cubic) and give the atomic
> positions of Zn and O as
> 
> 
> 
> 
>  Zn  0.000  0.000  0.000
> 
>  Zn  0.500  0.500  0.000
> 
>  Zn  0.500  0.000  0.500
> 
>  Zn  0.000  0.500  0.500
> 
>   O  0.250  0.250  0.250
> 
>   O  0.750  0.750  0.250
> 
>   O  0.750  0.250  0.750
> 
>   O  0.250  0.750  0.750
> 
> 
> 
> In this case BZ is simple cubic not
> FCC. Now my question is that
> is band gap will be same in both cases for ibrav = 2 and ibrav =1 as
> structure is same i.e
> zinc blende. But band structure is different. {because BZ is different for
> different ibarv}
> 
> 
> 
> 
> 
> 
> 
> 
> Muhammad Zafar
> 
> PhD Scholar
> 
> Department of Physics
> 
> The Islamia University of Bahawalpur,Pakistan

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   Giuseppe Mattioli                            
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