[Pw_forum] equilibrium lattice constant of magnetite

[bamidele ibrahim]

Dear Abolore,
Read this article it contains all the atomic positions for the compound. You need to know that for this compound Z=8.

http://www.springerlink.com/content/p27870432mt31374/fulltext.pdf

 
Adetunji Bamidele Ibrahim(PhD Student)
Department of physics,University of Agriculture,
Abeokuta, Ogun State,Nigeria.


________________________________
 From: Abolore Musari <abmus007 at gmail.com>
To: PWSCF Forum <pw_forum at pwscf.org> 
Sent: Monday, August 6, 2012 4:42 PM
Subject: Re: [Pw_forum] equilibrium lattice constant of magnetite
 

Thanks so much Jia
But Sir the atomic positions in the input is for 3 atoms, should l leave the atomic position and change the number of atom or my atomic position is wrong??
thanks
Musari A. A
UNAAB Nigeria


On Mon, Aug 6, 2012 at 3:34 PM, jia chen <jiachen at princeton.edu> wrote:

Dear Abolore Musari,
>
>
>I guess the number of atoms should be 14, instead of 3.
>
>
>Regards
>Jia
>
>
>On Mon, Aug 6, 2012 at 10:24 AM, Abolore Musari <abmus007 at gmail.com> wrote:
>
>Dear QE users
>>Sir, I am try to find the lattice constant of magnetite (Fe3O4) which is a spinel ferrimagnetic material. The expt lattice constant was 15.87 and I have been trying to find the equilibrium lattice constant (celldm(1)) between 15.80 - 16.00 and all i get is a straight line graph instead of the usual exponential curve graph. I have tried all l could most esp with starting_magnetization but the results are the same. My input is pasted below pls help me to get the appropriate graph.
>>The kind of the graph I got is attached.
>>Thanks
>>
>>&control
>>    calculation = 'scf',
>>    restart_mode ='from_scratch',
>>    prefix = 'Fe3O4',
>>    pseudo_dir = '/home/abolore/Programs/Pseudos/',
>>    outdir = './tmp/'
>> /
>> &system
>>    ibrav = 2, 
>>    celldm(1)= $15.80-16.00,
>>    nat = 3, 
>>    ntyp = 3,
>>    ecutwfc = 40,
>>    ecutrho = 400,
>>    starting_magnetization(1) = 0.7,
>>    starting_magnetization(2) = -0.5,
>>    starting_magnetization(3) = 0.0,
>>    nspin = 2,
>>    occupations='smearing',
>>    smearing='gaussian',
>>    degauss = 0.05,
>> /
>> &electrons
>>   diagonalization = 'david',
>>   mixing_mode = 'plain',
>>   mixing_beta = 0.7
>> /
>>ATOMIC_SPECIES
>>    Fe1     55.845   Fe.pz-nd-rrkjus.UPF
>>    Fe2     55.845      Fe.pz-nd-rrkjus.UPF
>>     O      16.000      O.pz-rrkjus.UPF
>>
>>ATOMIC_POSITIONS
>>Fe1 0.125  0.125  0.125  
>>Fe2 0.500  0.500  0.500
>>O    0.2548 0.2548 0.2548
>> 
>>K_POINTS (automatic)
>>  8 8 8 1 1 1
>>
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>>
>
>
>
>-- 
>Jia Chen
>
>
>
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