[Pw_forum] problem witch wurtzite structure

[ramzi alaya]

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
Faculté des Sciences de Gabès, Cité Erriadh 6072 Gabès- Tunisie
Unité de Recherche sur les Hétéro-Epitaxies et Applications

 		 	   		  
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