[QE-users] DFT relaxation steps

[Dr. SUNIL KUMAR]

Dear QE developers and Users.

We are doing DFT simulation of Monoclinic YNiO3 with and without oxygen
vacancy. During the vc-relax and relax relaxation step,  energy does not
converge and simulation ends with error msg " convergence NOT achieved
after 200 iterations: stopping" . I have tried many different values of
ecutwfc and mixing_beta but unable to find convergence. Your suggestions
will be highly appreciated.
Following is the script for QE.

Thank you

&CONTROL
    calculation   = "relax"
    prefix        = "espresso"
    wf_collect    = .TRUE.
    forc_conv_thr =  1.00000e-03
    max_seconds   =  1.72800e+05
    nstep         =  100
    pseudo_dir    = "/home/pseudopot"
    outdir        = "./outdir"
    wfcdir        = "./wfcdir"
/

&SYSTEM
    a                         =  5.17932e+00
    b                         =  5.51529e+00
    c                         =  7.41657e+00
    cosac                     = -1.34914e-03
    degauss                   =  1.00000e-02
    ecutrho                   =  2.25000e+02
    ecutwfc                   =  2.50000e+01
    ibrav                     = -12
    nat                       = 19
    nspin                     = 2
    ntyp                      = 3
    occupations               = "smearing"
    smearing                  = "gaussian"
    starting_magnetization(1) =  2.00000e-01
    starting_magnetization(2) =  0.00000e+00
    starting_magnetization(3) =  2.00000e-01
/

&ELECTRONS
    conv_thr         =  1.00000e-06
    electron_maxstep = 200
    mixing_beta      =  4.00000e-01
    startingpot      = "atomic"
    startingwfc      = "atomic+random"
/

&IONS
    ion_dynamics = "bfgs"
/

&CELL
/

K_POINTS {automatic}
 2  2  2  0 0 0

ATOMIC_SPECIES
Ni     58.69340  Ni.pz-mt_fhi.UPF
O      15.99940  O.pz-mt_fhi.UPF
Y      88.90585  Y.pz-mt_fhi.UPF

ATOMIC_POSITIONS {angstrom}
Ni      2.589660   0.000000   0.000000
Ni      0.000000   2.757645   0.000000
Ni     -0.005000   0.000000   3.708280
Ni      2.584660   2.757645   3.708280
O       1.796655   1.696862   0.356885
O       1.238791   4.384435   0.375842
O       0.756099   2.606316   1.812340
O       4.418221   5.363961   1.895940
O       3.935529   1.626790   3.332439
O       3.377665   4.454507   3.351395
O       1.233790   3.888500   4.084122
O       0.751099   0.151329   5.520620
O       4.413221   2.908974   5.604220
O       3.930529   1.130855   7.040719
O       3.372665   3.818428   7.059675
Y       3.782084   3.157134   1.851618
Y       1.392236   0.399489   1.856662
Y       3.777084   5.115801   5.559899
Y       1.387236   2.358156   5.564942


Dr. Sunil Kumar
Ph.D (Chemical Engg. IIT Delhi)
M.Tech (Chemical Engg. IIT Delhi)
B.Tech (Chemical Engg. IET-CSJMU Kanpur)
Senior Scientist (E1) and Assistant Professor
CSIR-National Metallurgical Laboratory Jamshedpur-831007
http://www.nmlindia.org/
https://scholar.google.co.in/citations?user=OchYqugAAAAJ&hl=en&oi=sra
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