[Pw_forum] Default value of nbnd for GaAs

[Krishnendu Ghosh]

You included semicore d states from Ga. That's giving 5 orbitals.
On Aug 1, 2016 1:24 PM, "Mohammad Abu Raihan Miah" <mraihanm at eng.ucsd.edu>
wrote:

> Hi all,
>
> I am currently doing simulation to calculate the band structure of GaAs. I
> use the basic primitive cell to simulate.
>
> In order to calculate the band structure I need to specify the number of
> bands, nbnd parameter. Now as far as I understand, For GaAs there are 4
> valence electrons per atom. So for a 2 atom primitive cell, the default
> value of nbnd should be 4. But instead I get the default value of nbnd as 9
> (I checked the value from output file as for each k, 9 eigen energy value
> is calculated)
>
> My input file as follows:
>
>
> &CONTROL
>   calculation='scf',
>   outdir='out_bulk',
>   prefix='GaAs_2',
>   pseudo_dir='.',
>   verbosity='low',
>   tstress=.false.,
>   tprnfor=.false.,
> /
>
> &SYSTEM
>   ibrav=2,
>   celldm(1)=10.6839445905d0,
>   nat=2,
>   ntyp=2,
>   ecutwfc=50.0d0,
>   ecutrho=400.0d0,
>   input_dft='PBE',
> /
>
> &ELECTRONS
>   diagonalization='david',
>   conv_thr=1d-06,
>   mixing_mode='plain',
>   mixing_beta=0.700d0,
> /
>
> ATOMIC_SPECIES
>   As 74.921600d0 As.pbe-n-rrkjus_psl.0.2.UPF
>   Ga 69.723000d0 Ga.pbe-dn-rrkjus_psl.0.2.UPF
>
> ATOMIC_POSITIONS {alat}
>   Ga   0.0000000000d0   0.0000000000d0   0.0000000000d0
>   As   0.2500000000d0   0.2500000000d0   0.2500000000d0
>
> K_POINTS {automatic}
>   8 8 8 0 0 0
>
>
> Could anyone please explain that to me?
>
> Thank you very much.
>
> Best,
> --
> Mohammad Abu Raihan Miah
> PhD Student
> Department of Electrical and Computer Engineering (ECE)
> <http://www.ece.ucsd.edu/>
> University of California, San Diego <http://www.ucsd.edu/>
>
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