[Pw_forum] a question about MnSe

[jia chen]

Dear All,

I also have a question about vc-relax. How do you know if your cutoff is
large enough to overcome Pulay stress, or you can do something else to get
rid of it in you calculations. Thanks.

Best Wishes
jia

On Wed, Jan 19, 2011 at 11:57 AM, mohnish pandey <mohnish.iitk at gmail.com>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
>
> *OUTPUT FOR ROCKSALT*
>
>  bfgs converged in   8 scf cycles and   4 bfgs steps
>      (criteria: energy < 0.10E-03, force < 0.10E-02, cell < 0.50E+00)
>
>      End of BFGS Geometry Optimization
>
>      Final enthalpy =    -464.4688263706 Ry
> Begin final coordinates
>      new unit-cell volume =    533.55466 a.u.^3 (    79.06464 Ang^3 )
>
> CELL_PARAMETERS (alat= 10.30260000)
>    0.494008772   0.494008772   0.990589056
>    0.494008772   0.990589056   0.494008772
>    0.990589056   0.494008772   0.494008772
>
> ATOMIC_POSITIONS (crystal)
> Se       0.249999854   0.249999854   0.249999854
> Se       0.750000146   0.750000146   0.750000146
> Mn1      0.000000000   0.000000000   0.000000000
> Mn2      0.500000000   0.500000000   0.500000000
> End final coordinates
>
> *INPUT FOR WURTZITE*
>
> &control
>     calculation = 'vc-relax',
>     restart_mode='restart',
>     verbosity = 'high'
>     wf_collect = .true.
>     outdir='/home/mohnish/mnse-wurtzite-bulk',
>     pseudo_dir='/home/mohnish/mnse-wurtzite-bulk'
>     prefix='mnse',
>     tstress = .true.,
>     tprnfor = .true.,
> /
>  &system
>     ibrav=  4, a = 4.178, c = 6.783,nat= 4, ntyp= 3,
>     ecutwfc =
> 40,ecutrho=320,occupations='smearing',degauss=0.01,smearing='gaussian',
>     nspin =2,starting_magnetization(1)=0.5,starting_magnetization(2)=
> -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
>   Mn1 54.938 Mn.pbe-sp-van_mit.UPF
>   Mn2 54.938 Mn.pbe-sp-van_mit.UPF
>   Se  78.960 Se.pbe-van.UPF
> ATOMIC_POSITIONS (crystal)
>   Mn1  0.000000000  0.000000000000  0.000000000
>   Mn2  0.333333333  0.666666666667  0.500000000
>   Se   0.000000000  0.000000000000  0.345000000
>   Se   0.333333333  0.666666666667  0.845000000
>  K_POINTS (automatic)
>  6 6 4 0 0 0
>
> *OUTPUT FOR WURTZITE*
>
>  End of BFGS Geometry Optimization
>
>      Final enthalpy =    -464.4799667612 Ry
> Begin final coordinates
>      new unit-cell volume =    681.36082 a.u.^3 (   100.96726 Ang^3 )
>
> CELL_PARAMETERS (alat=  7.89527578)
>    1.001414763   0.000000000   0.000000000
>   -0.500707382   0.867250625   0.000000000
>    0.000000000   0.000000000   1.594103933
>
> ATOMIC_POSITIONS (crystal)
> Mn1      0.000000000   0.000000000  -0.014999731
> Mn2      0.333333333   0.666666667   0.485592670
> Se       0.000000000   0.000000000   0.359333481
> Se       0.333333333   0.666666667   0.860073579
> End final coordinates
>
>
>
>
>
> --
> Regards,
> MOHNISH,
> -----------------------------------------------------------------
> Mohnish Pandey
> Y6927262,5th Year dual degree student,
> Department of Chemical Engineering,
> IIT KANPUR, UP, INDIA
> -----------------------------------------------------------------
>
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>


-- 
Jia Chen
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