[Pw_forum] a question about MnSe

[mohnish pandey]

Dear Michael!
                         To get an AFM ground state we I think we should
have atleast two Mn atom. I did the calculation for Rocksalt symmetry but it
was also not giving proper results.

On Wed, Jan 19, 2011 at 11:52 PM, Mike Mehl <Michael.Mehl at nrl.navy.mil>wrote:

> Two things:
>
> First,
>
> Having atoms designated Mn1 and Mn2 reduces the symmetry from Fm(3-)m
> (cubic rocksalt) to R(-3)m (rhombohedral), which is why you see a
> rhombohedral lattice in the output for the rocksalt structure.
>
> Second,
>
> What answer do you get when you use the primitive cell for the Rocksalt
> structure, rather than one that looks rhombohedral?
>
> CELL_PARAMETERS (cubic)
>  0.0 0.5 0.5
>  0.5 0.0 0.5
>  0.5 0.5 0.0
>
> ATOMIC_POSITIONS (crystal)
> Se       0.00 0.00 0.00
> Mn       0.50 0.50 0.50
>
>
> On 01/19/2011 11:57 AM, mohnish pandey wrote:
> > Dear QE users,
> >                             I am trying to do bulk calculations for MnSe
> > in rocksalt and wurtzite structure. Its has AFM ground state in rocksalt
> > structure but after checking convergence I am finding "rocksalt"
> > structure to be energetically higher than wurtzite structure. I am
> > pasting my segments of input and output files. Can anybody please help
> > me in figuring out the problem.
> >
> > *INPUT FOR ROCKSALT*
> >
> > &control
> >      calculation = 'vc-relax'
> >      restart_mode='restart',
> >      wf_collect = .true.
> >      prefix='mnse',
> >      pseudo_dir = '/home/mohnish/mnse-rocksalt-bulk',
> >      outdir='/home/mohnish/mnse-rocksalt-bulk',
> >      tprnfor = .true.,
> >      tstress=.true.
> >   /
> > &system
> >      ibrav=  0, celldm(1)= 10.3026, nat=  4, ntyp= 3,
> >      ecutwfc = 40.0, ecutrho = 320.0,
> >      occupations='smearing', smearing='gauss', degauss=0.01,
> >      nspin=2,
> >      starting_magnetization(1)= 0.0,
> >      starting_magnetization(2)= 0.5,
> >      starting_magnetization(3)=-0.5,
> >   /
> > &electrons
> >     diagonalization='david'
> >     mixing_mode = 'plain'
> >     mixing_beta = 0.4
> >     conv_thr = 1.0d-8
> >     startingpot = 'file'
> >     startingwfc = 'file'
> >   /
> > &IONS
> >    ion_dynamics='bfgs'
> >    trust_radius_max = 0.40
> >    trust_radius_ini = 0.20
> > /
> > &CELL
> >    cell_dynamics='bfgs',
> > /
> > ATOMIC_SPECIES
> >    Se  78.960 Se.pbe-van.UPF
> >    Mn1 54.938 Mn.pbe-sp-van_mit.UPF
> >    Mn2 54.938 Mn.pbe-sp-van_mit.UPF
> > CELL_PARAMETERS
> > 0.50 0.50 1.00
> > 0.50 1.00 0.50
> > 1.00 0.50 0.50
> > ATOMIC_POSITIONS {crystal}
> >   Se  0.25 0.25 0.25
> >   Se  0.75 0.75 0.75
> >   Mn1 0.0  0.0  0.0
> >   Mn2 0.5  0.5  0.5
> > K_POINTS {automatic}
> > 6 6 6 0 0 0
>
>
>
> --
> Michael J. Mehl
> Head, Center for Computational Materials Science
> Naval Research Laboratory Code 6390
> Washington DC
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>



-- 
Regards,
MOHNISH,
-----------------------------------------------------------------
Mohnish Pandey
Y6927262,5th Year dual degree student,
Department of Chemical Engineering,
IIT KANPUR, UP, INDIA
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