[Pw_forum] equilibrium lattice constant of magnetite

[jia chen]

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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