[QE-users] Relaxation of Fe2O3

[Anuja Chanana]

Dear users,
I am trying to relax the bulk structure of alpha-Fe2O3 in the rhombohedral
crystal structure. The ground state is +--+. However, the crystal lattice
doesn't relax and the total energy values keep fluctuating rather than
showing any convergence. The following is the input file

&CONTROL
    calculation = 'vc-relax',
    restart_mode = 'from_scratch',
    title = 'Fe2O3',
    prefix = 'Fe2O3',
    outdir = './tmp_Fe2O3_rhom_scf_1',
    pseudo_dir = '.',
    forc_conv_thr = 1.0D-5,
    tprnfor = .true.,
    tstress = .true.
    verbosity = 'high'
    wf_collect = .true.,
    nstep = 1000,
/

&SYSTEM
  ibrav=5,
  celldm(1)=10.2528224724d0, celldm(4)=0.5694631780d0,
  nat=10,
  ntyp=5,
  ecutwfc = 80,
  ecutrho = 640,
  occupations='smearing'
  smearing='fd'
  degauss= 0.005,
  nspin=2,
  starting_magnetization(1)= 0.0,
  starting_magnetization(2) =  1.0,
 starting_magnetization(3) =  -1.0,
 starting_magnetization(4) =  -1.0,
 starting_magnetization(5) =   1.0,
  lda_plus_u = .true.
  Hubbard_U(2) = 3.8
  Hubbard_U(3) = 3.8
  Hubbard_U(4) = 3.8
  Hubbard_U(5) = 3.8
/

&ELECTRONS
    mixing_beta = 0.2,
    conv_thr = 1.0D-6,
electron_maxstep=1000,
/
 &ions
 /

 &cell
/

ATOMIC_SPECIES
  O 15.999400d0 O.pw91-n-rrkjus_psl.1.0.0.UPF
  Fe1 55.845000d0 Fe.pw91-spn-rrkjus_psl.1.0.0.UPF
  Fe2 55.845000d0 Fe.pw91-spn-rrkjus_psl.1.0.0.UPF
  Fe3 55.845000d0 Fe.pw91-spn-rrkjus_psl.1.0.0.UPF
  Fe4 55.845000d0 Fe.pw91-spn-rrkjus_psl.1.0.0.UPF

ATOMIC_POSITIONS {crystal}
   O   0.9444650930d0   0.5556659533d0   0.2500659533d0
   O   0.2500650930d0   0.9444659533d0   0.5556659533d0
   O   0.0557952789d0   0.4445978598d0   0.7501978598d0
   O   0.4445952789d0   0.7501978598d0   0.0557978598d0
   O   0.5556650930d0   0.2500659533d0   0.9444659533d0
   O   0.7501952789d0   0.0557978598d0   0.4445978598d0
  Fe1   0.1446976654d0   0.1446981632d0   0.1446981632d0
  Fe2   0.6448278513d0   0.6448300697d0   0.6448300697d0
  Fe3   0.3554325205d0   0.3554337433d0   0.3554337433d0
  Fe4   0.8555627065d0   0.8555656499d0   0.8555656499d0

K_POINTS {automatic}
  8 8 8 0 0 0


Has anyone ever tried relaxing the structure before and faced a similar
situation?
What is the best possible solution if the system doesn't show a smooth
convergence.
Looking forward to a reply.

Thanks and Regards
Anuja Chanana



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07/28/19,
09:35:20 PM
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