[QE-users] error in scf calculation using wyckoff positions

[Pooja Vyas]

I tried to compute energy of antiferromagnetic (AFM) V3Al using the below
script:


&CONTROL
  calculation = 'scf'
  prefix = 'v3al'
  outdir = './'
  pseudo_dir = './'
  tprnfor = .true.
  tstress = .true.
  etot_conv_thr =   4.0000000000d-05
  forc_conv_thr =   1.0000000000d-04
  verbosity = 'high'
/

&SYSTEM
  ibrav = 0
! celldm(1) = 11.512210722
! space_group = 225
  nat = 16
  ntyp = 3
  ecutwfc = 60
  ecutrho = 400
  occupations = 'smearing'
  smearing = 'cold'
  degauss = 0.005
  nspin = 2
  starting_magnetization(1)=1
  starting_magnetization(2)=-1
  starting_magnetization(3)=1
  starting_magnetization(4)=-1
  starting_magnetization(5)=1
  starting_magnetization(6)=-1
  starting_magnetization(7)=1
  starting_magnetization(8)=-1
/

&ELECTRONS
  conv_thr =   8.0000000000d-10
  mixing_beta =   4.0000000000d-01
/

ATOMIC_SPECIES
Al 26.9815 Al.pbe-nl-rrkjus_psl.1.0.0.UPF
V1 50.9415 V.pbe-spnl-rrkjus_psl.1.0.0.UPF
V2 50.9415 V.pbe-spnl-rrkjus_psl.1.0.0.UPF

ATOMIC_POSITIONS {crystal}
V2            0.2500000000       0.2500000000       0.7500000000
V2            0.2500000000       0.2500000000       0.2500000000
V2            0.7500000000       0.7500000000       0.7500000000
V2            0.7500000000       0.7500000000       0.2500000000
V2            0.7500000000       0.2500000000       0.7500000000
V2            0.2500000000       0.7500000000       0.2500000000
V2            0.2500000000       0.7500000000       0.7500000000
V2            0.7500000000       0.2500000000       0.2500000000
Al            0.0000000000       0.0000000000       0.0000000000
Al            0.0000000000       0.5000000000       0.5000000000
Al            0.5000000000       0.0000000000       0.5000000000
Al            0.5000000000       0.5000000000       0.0000000000
V1            0.5000000000       0.5000000000       0.5000000000
V1            0.5000000000       0.0000000000       0.0000000000
V1            0.0000000000       0.5000000000       0.0000000000
V1            0.0000000000       0.0000000000       0.5000000000

K_POINTS automatic
  10 10 10 0 0 0

CELL_PARAMETERS angstrom
6.092 0.000 0.000
0.000 6.092 0.000
0.000 0.000 6.092

-------------------------------------------------------------------------

But as the iterations proceed, I see that the values of total and absolute
magnetisation both approaches zero value.
     total magnetization       =     0.03 Bohr mag/cell
     absolute magnetization    =     0.14 Bohr mag/cell (This is at 27th
iteration and calculation is still going as energy is not yet converged.
So, at final iteration, probably both will become zero)

Shouldn't atleast the absolute magnetisation be nonzero value? I guess for
AFM, only total magnetisation at the end should be zero.
I'm saying this because when I had performed AFM calculation for chromium,
total magnetisation was 0.0 but absolute was 2.28 bohr mag/cell.
are things going correct? Attached below is the cif file.



On Tue, Jun 18, 2024 at 4:14 PM Paolo Giannozzi <paolo.giannozzi at uniud.it>
wrote:

> On 6/18/24 08:59, Pooja Vyas wrote:
>
> >    space_group = 225
>
> > ATOMIC_POSITIONS {crystal_sg}
> > Al 4a
> > V1 4b
> > V2 8c
> > V3 0.25 0.25 0.75
>
> >       Error in routine check_atoms (1):
> >       atoms #   3 and #   6 overlap!
>
> they do: atom V3 overlaps with one of the two positions for atoms V2.
> See https://www.cryst.ehu.es/cgi-bin/cryst/programs/nph-wp-list for
> group 225.
>
> 4a = 4 atoms in the conventional cell (cubic), 1 atom in the primitive
> cell (fcc). Same for 4b and 8c. So you have nat=3 (number of Wyckoff
> positions, not of atoms) and 4 atoms, 1 Al and 3 V, if you set
> ATOMIC_POSITIONS {crystal_sg}
> Al 4a
> V1 4b
> V2 8c
> Note that ntyp=3: there are two different types of V atoms, not three.
> Disclaimer: just guessing
>
> Paolo
>
> >       stopping ...
> >
> >
> >
> >
> ----------------------------------------------------------------------------
> >
> > What is causing the issue and what should be changed in the input file?
> > Any kind of help is appreciated.
> >
> >
> > *Pooja,
> > *
> > *Research Scholar,*
> > *Department of Physics,*
> > *MKBU,*
> > *Bhavnagar,*
> > *Gujarat.*
> > *
> > *
> >
> > _______________________________________________
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> --
> Paolo Giannozzi, Dip. Scienze Matematiche Informatiche e Fisiche,
> Univ. Udine, via delle Scienze 206, 33100 Udine Italy, +39-0432-558216
> X SCUOLA ESTIVA DI ENERGIE RINNOVABILI
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