[Pw_forum] equilibrium lattice constant of magnetite

[Abolore Musari]

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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