[Pw_forum] The coordinate of X-point in GaAs band structure calculation

[Stefano de Gironcoli]

The one you are using: ibrav=1.
Do not expect to see a band structure similar to the usual one tho

stefano 
(sent from my phone)

> On 31 Oct 2016, at 03:03, evan <ewan26 at 126.com> wrote:
> 
> Dear Stefano and Andrew
> 
> Thank you for your kind replies. Let me ask a more general question which I think about.
> 
>  I want to calculate the band structure of GaAs (FCC structure) in a simple cubic lattice cell with eight atoms (ibrav =1). If I specify the k points in units of 2pi/a (K_POINTS tpiba_b), the high symmetry points in Brillioun zone of which cell I should specify in the input file, FCC (ibrav =2) or those of SC (ibrav=1) lattice structure?
> 
> If I specify the k points in in crystal coordinates (K_POINTS crystal_b), then of which cell I should specify the k points in the input files, FCC or SC lattice structure.
> 
> Thank you in advance.
> 
> Regards
> 
> Evan
> 
> USC, China
> 
> 
> At 2016-10-30 02:17:33, "stefano de gironcoli" <degironc at sissa.it> wrote:
> Dear Evan,
>    GaAS structure is zincblend (2 atoms per cell). its X point is indeed 2pi/a(1,0,0).
>    if you choose to compute GaAs in a SC cell (8 atoms pr cell) then that point is indeed equivalent to Gamma. The zone boundary of the SC cell is pi/a(1,0,0) but this of course does not correspond to the X point of the zincblend structure.
>   HTH
>  stefano
> 
>> On 29/10/2016 16:00, evan wrote:
>> Hello, everyone
>> 
>> I calculated the band structure of GaAs in a simple cubic lattice cell (ibrav=1), I searched from the internet the coordinates of X-point in the first Brillouin zone are 2pi/a(0,0,1) or 2pi/a(1,0,0), but both results show that band gap occurs at G and X points simultaneously, it seems to me that the X is equivalent to G, can you tell me the correct X point coordinates which give me the reasonable result. The input files and results are attached, you can show what is wrong in the input file.
>> 
>> Your suggestions are appreciated.
>> 
>> Yours sincerely
>> 
>> Evan
>> 
>> USC, China 
>> 
>> 
>> 
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>> 
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