[QE-users] DFT relaxation steps

[Giuseppe Mattioli]

Dear Sunil Kumar
Check the structure first. I opened your file with xcrysden and even  
if it is not totally weird, it is a bit strange (Ni-Y distances of 2.2  
A are likely wrong...). Moreover, are you sure you want to use the LDA  
(PZ) functional? The electronic structure of a TM oxide will likely be  
strongly affected by delocalization errors. Finally, I expect that you  
norm-conserving (so no need to specify ecutrho, it has a fixed value  
of 4*ecutwfc) mt-fhi pseudopotentials are quite hard, with ecutwfc  
maybe as high as 120-140 Ry. In difficult cases (but check the  
structure first!) you may lower mixing_beta down to 0.01.
HTH
Giuseppe

Quoting "Dr. SUNIL KUMAR" <suniliitd14 at gmail.com>:

> 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



GIUSEPPE MATTIOLI
CNR - ISTITUTO DI STRUTTURA DELLA MATERIA
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E-mail: <giuseppe.mattioli at ism.cnr.it>