[QE-users] DFT convergence problem

[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 
https://scholar.google.co.in/citations?user=OchYqugAAAAJ&hl=en&oi=sra 
Mobile: 7541810554, 06572345029 



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