[Pw_forum] wurtzite AlN

[Marcel Mohr]

Hi,

wurtzite has 4 atoms in the unit cell.

Cheers Marcel


On Tue, 15 Jan 2008, Helen wrote:

> Hi,
> I've successfully calculated the bandstructure for zinc-blende AlN, and I wanted to do the same for wurtzite AlN but am running into problems. I started off with a=5.88 a.u. c/a=1.600 and u=0.382 , I then kept a and c constant and altered u. The results showed that u needed to be smaller but when I reached u=0.369 my scf calculations stopped converging. I tried using both cg and davidson diagonalization. I then tried keeping u constant and altering c, I don't get convergence problems but I get unrealistically small values of c. Also the bandgap data I'm getting is nonsense (no band gap at all). Perhaps I have a mistake in my input file?
> Thank you for your help and advice,
> Dr. Helen Eisenberg (Fritz Haber Center, Hebrew University)
>
> &control
>    calculation='scf'
>    restart_mode='from_scratch',
>    tstress = .true.
>    tprnfor = .true.
>    prefix='alas',
>    pseudo_dir = '$PSEUDO_DIR/',
>    outdir='$TMP_DIR/'
> /
> &system
>    ibrav=  4, celldm(1) =5.88, celldm(3)=1.600, nat=  2, ntyp= 2,
>    ecutwfc =80.0, nbnd = 8,
>    nr1=32,
>    nr2=32,
>    nr3=32,
>    ecutrho = 240.0
> /
> &electrons
>    conv_thr =  1.0d-6
>    mixing_beta = 0.7
> /
> ATOMIC_SPECIES
> Al  26.98  Al.vbc.UPF
> N   14.007  N.pz-vbc.UPF
> ATOMIC_POSITIONS
> Al 0.00 0.00 0.00
> N 0.00 0.00 0.611
> K_POINTS (automatic)
> 4 4 4 0 0 0
> EOF