! E10: FeO in the rocksalt structure with AFM-II order
! (ferromagnetic (111) planes with alternating sign).
! The magnetic unit cell is rhombohedral: 2 Fe + 2 O, volume = 0.5 a^3.
! THE POINT of this run: the AFM order converges beautifully, and GGA
! still predicts a metal. Experiment says insulator, gap ~2.4 eV.

&CONTROL
  calculation = 'scf'
  prefix      = 'FeO'
  outdir      = './tmp/'
  pseudo_dir  = './pseudo/'
  verbosity   = 'high'        ! also prints the ns matrices once U is on (E11)
  tprnfor     = .true.
  tstress     = .true.
/
&SYSTEM
  ibrav       = 0             ! cell given explicitly below
  celldm(1)   = 8.18          ! cubic a in bohr (= 4.33 Angstrom); scales CELL_PARAMETERS (alat)
  nat         = 4
  ntyp        = 3             ! Fe1, Fe2, O: the label split that makes AFM possible
  ecutwfc     = 70
  ecutrho     = 700           ! the 10x Fe rule again
  occupations = 'smearing'    ! the GGA ground state is (wrongly) metallic, so smear
  smearing    = 'mv'
  degauss     = 0.01
  nspin       = 2
  starting_magnetization(1) =  0.6    ! Fe1 sublattice: up
  starting_magnetization(2) = -0.6    ! Fe2 sublattice: down  -> AFM seed
  starting_magnetization(3) =  0.0    ! O: no seed
/
&ELECTRONS
  conv_thr    = 1.0d-8
  mixing_beta = 0.2           ! touchy magnetic oxide: mix gently
  mixing_mode = 'local-TF'
  electron_maxstep = 300
/

! the SAME pseudopotential file under two labels: without this split QE
! treats the two Fe as symmetry-equivalent and no AFM state can form
ATOMIC_SPECIES
  Fe1  55.845  Fe.pbe-spn-kjpaw_psl.1.0.0.UPF
  Fe2  55.845  Fe.pbe-spn-kjpaw_psl.1.0.0.UPF
  O    15.999  O.pbe-n-kjpaw_psl.1.0.0.UPF

! rhombohedral doubling of the fcc cell along [111], in units of alat:
! these three vectors hold two rocksalt formula units, so that the two Fe
! (111) planes can carry opposite spins. det = 0.5 -> volume 0.5 a^3.
CELL_PARAMETERS (alat)
  0.5  0.5  1.0
  0.5  1.0  0.5
  1.0  0.5  0.5

! fractional coordinates: Fe at 0 and 1/2 along the cell diagonal are the
! two oppositely magnetized (111) planes; O sits between them
ATOMIC_POSITIONS (crystal)
  Fe1  0.00  0.00  0.00
  Fe2  0.50  0.50  0.50
  O    0.25  0.25  0.25
  O    0.75  0.75  0.75

K_POINTS (automatic)
  6 6 6  0 0 0