[Pw_forum] QE & Xcrysden

[Ngoc Linh Nguyen]

naphtaly moro wrote:
> Dear Q.E. & Xcrysden
> I am working on the various phase transitions of GaAs. I am trying to
> contact these structures. I ahve managed to construct the ZB and RS
> structures with success. I am using Xcrysden with Quantum Espresso.
> When i try to view the CsCl-GaAs structure,  I only see the Ga atoms
> and with no As atoms in the matrix. Can someone show me please where I
> am going wrong
>  my input file is this
>  &control
>    prefix='GaAs',
>    pseudo_dir='/home/physics/Desktop/espresso-4.0.5/pseudo'
>    outdir = './tmp',
>  /
>  &system
>    ibrav=  3, celldm(1) =10.2, nat=  2, ntyp= 2,
>    ecutwfc = 12.0,
>  /
>  &electrons
>  /
> ATOMIC_SPECIES
>  Ga  69.723  Ga.pbe-nsp-van.UPF
>  As  74.9216 As.pbe-n-van.UPF
> ATOMIC_POSITIONS
>  Ga 0.00 0.00 0.00
>  As 0.50 0.50 0.50
> K_POINTS {automatic}
>  4 4 4 0 0 0
>
>   
You are having a wrong input structure. Namely, you chose ibrav= 3 which 
means BCC lattice, so in a periodic lattice the As atoms will be 
overlapped by Ga atoms.

How to fix the problem. You should again pick up another ibrav value and 
calculate the Gs and As positions.
As far as I know, GaAs lattice have a similarity to diamond lattice, so 
I suggest ibrav=2, and

Ga 0.00 0.00 0.00
As 0.25 0.25 0.25

Good luck

Linh


> Thanks
>
>
>   


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