[Pw_forum] GaAs Band structure

[lan haiping]

Hi,
Several comments:
1, it seems you use  NCPP pseudopotentials . Therefore , 40 Ry for enenrgy
cutoff is not enough to get convergent results.
2, You can do alignment of so-called fermi level,  which is meaningless
since you deal with a semiconductor.
3, Underestimation of energy gap is well accepted in LDA calculations.


Hope helps

Regards

On Fri, Aug 28, 2009 at 3:37 AM, nand <rana_nand at yahoo.com> wrote:

>
>
> Sir,
> I am a research scholar at the Ranchi university, India. It will be a great
> help if you can help me with the band structure calculation for GaAs using
> Quantum Espresso.
> I do not get the correct band structure  even with the input file you
> mentioned below. I am attaching the band structure pdf file which I produced
> using  input file given below. As you can see that the fermi level is
> wrongly located and the band gap is badly  underestimated. Please tell me
> about the possible fault(s) possible in my calculation.
> Thanking you in advance.
> Nand Rana,
> (Research Scholar)
> Ranchi, India.
>
> -----------------------------------
> input file for the scf calculation:
>
> &control
>   calculation='scf',
>   outdir='./tmp',
>   prefix='gaas',
>   pseudo_dir='/espresso-4.0.4/pseudo'
> /
>
> &system
>   ibrav=2,
>   celldm(1)=10.6827,
>   nbnd=8,
>   nat=2,
>   ntyp=2,
>   ecutwfc=40.0d0,
>   occupations='fixed',
>   nspin=1
> /
>
> &electrons
>   conv_thr=1d-6,
>   mixing_beta=0.7,
>   diagonalization='david'
> /
>
> ATOMIC_SPECIES
>  Ga   69.723   Ga.pz-bhs.UPF
>  As   74.92160 As.pz-bhs.UPF
>
> ATOMIC_POSITIONS  alat
>   Ga 0.0   0.0   0.0
>   As 0.25  0.25  0.25
>
> K_POINTS   automatic
>    10 10 10 0 0 0
>
>
>
>
>
>
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>


-- 
Hai-Ping Lan
Department of Electronics ,
Peking University , Bejing, 100871
lanhaiping at gmail.com, hplan at pku.edu.cn
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