default setting for atomic coordinates is "alat", tha is cartesian 
coordinates in unit of alat...
you probably want "crystal" setting.
visualize the structure by Xcrysden to see the difference

stefano

On 06/06/2012 03:00 PM, ramzi alaya wrote:
> Dear all,
>
> I've tried calculated the bandstructure for Wurtzite AlN but am running into 
> problems. I started off with experimental values ( a=5.87 a.u. c/a=1.60 and 
> u=0.379), I then kept
> a and u constant and altered c/a. I found an unrealistically small value c/a 
> ( c=0.9). I then tried keeping c/a constant and altering a my scf 
> calculations stopped converging. Perhaps I have a mistake in my input file?
> Thank you for your help and advice.
> This is the input file for the "scf" calculation
>
> &control
>      calculation='scf'
>      restart_mode='from_scratch',
>      tstress = .true.
>      tprnfor = .true.
>      prefix='810-28',
>      pseudo_dir = '/home/projet/pseudo/',
>      outdir='/home/projet/tp/'
>   /
>   &system
>      ibrav=  4, celldm(1) =8.12, celldm(3) =0.9, nat= 4, ntyp= 2,
>      ecutwfc =50.0, ecutrho = 600.0,
>   /
>   &electrons
>      diagonalization='david'
>      conv_thr = 1.0e-6
>      mixing_beta = 0.7
>   /
> ATOMIC_SPECIES
>   al  26.9815 al_pz.upf
>   n  14.0067 n_pz.upf
> ATOMIC_POSITIONS
>   al  0.333333333  0.666666667  0.000000000
>   al  0.666666667  0.333333333  0.500000000
>   n   0.333333333  0.666666667  0.379000000
>   n   0.666666667  0.333333333  0.879000000
> K_POINTS (automatic)
>   6 6 4 1 1 1
>
>
>
> ****************************************************************************************************************************************************************************
> Ramzi Alaya
> E-mail : ramzialaya at hotmail.fr
> Facult? des Sciences de Gab?s, Cit? Erriadh 6072 Gab?s- Tunisie
> Unit? de Recherche sur les H?t?ro-Epitaxies et Applications
>
>                                       
>
>
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