[Pw_forum] wurtzite AlN

[Helen]

Thank you! I'm now reading up on the wurtzite unit cell to make sure I get 
my input file correct,
Helen

----- Original Message ----- 
From: "Marcel Mohr" <marcel at physik.tu-berlin.de>
To: "PWSCF Forum" <pw_forum at pwscf.org>
Sent: Tuesday, January 15, 2008 1:07 PM
Subject: Re: [Pw_forum] wurtzite AlN


> 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
>
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