[QE-users] extrapolated charge too large during vc-relax leading to too many energy bands not converged error

Lucian D. Filip lucian.filip at infim.ro
Mon Jul 25 21:45:49 CEST 2022


Hello all,

I have stumbled on a problem that is very frustrating and cannot figure 
out what is happening. I am trying to do a vc-relax of a rather large 
structure 115 atoms. It constits of 
3-SrRuO3/7-PbTiO3/3-SrTiO3/7-PbTiO3/3-SrRuO3. The numbers in front of 
the materials represent the number of unit cells of each material. The 
structure is 1x1x23. I have tried both with vacuum on either side (about 
15 A because if I add more then the FFT limit is reached and I get that 
error) and in super cell configuration (i.e. no vacuum) but the same 
thing happens:

The calculation starts  and the first scf step converges in 240 
iterations. I know it is a large number but the structure is also large 
and I have seen that this is quite common for these cases. I may be 
wrong thou... The starting charge is  951.8694, renormalised to     
952.0000. All is good and the first step converges. Then in the second 
step starts the weird part:

extrapolated charge  991.00311, renormalised to  952.00000

Then it tries to perform the first scf step and the calculation dies 
with the:

Error in c_bands(1):

too many bands are not converged

I do not understand what is happening because I have succesfully relaxed 
slightly smaller but similar structures: 
3-SrRuO3/7-PbTiO3/3-SrTiO3/3-SrRuO3 and 3-SrRuO3/7-PbTiO3/3-SrRuO3. 
These two I relaxed with 15A of vacuum on either side.


I am using ultrasoft PBE PPs.

Here is the input I used:


&control
  calculation         = 'vc-relax'
  restart_mode        = 'from_scratch'
  prefix              = '10Fd-3i-10Fd-slab'
  disk_io             = 'low'
  tstress             = .true.
  tprnfor             = .true.
  etot_conv_thr       = 1.e-4
  forc_conv_thr       = 1.e-4
  verbosity           = 'high'
  pseudo_dir          = '../pp/pbe-US/'
  outdir              = '10Fd-3i-10Fd-slab'
  nstep               = 600
/

&system
  ibrav               = 6
  celldm(1)           = 7.37937998548
  celldm(3)           = 28.8910838525
  nat                 = 115
  ntyp                = 5
  ecutwfc             = 60.
  ecutrho             = 480.
  occupations         = 'smearing'
  degauss             = 0.01
  smearing            = 'gaussian'
/

&electrons
  diagonalization     = 'david'
  mixing_beta         = 0.1
  mixing_mode         = 'local-TF'
  conv_thr            = 1.e-8
  scf_must_converge   = .false.
  electron_maxstep    = 400
/

&ions
  ion_dynamics        = 'bfgs'
/

&cell
  cell_dynamics       = 'bfgs'
/

ATOMIC_SPECIES
  Pb    1              Pb.pbe-dn-rrkjus_psl.0.2.2.UPF
  Ti    1              Ti.pbe-spn-rrkjus_psl.1.0.0.UPF
  O     1               O.pbe-n-rrkjus_psl.0.1.UPF
  Sr    1              Sr.pbe-spn-rrkjus_psl.1.0.0.UPF
  Ru    1              Ru.pbe-n-van.UPF

ATOMIC_POSITIONS {angstrom}
Sr  0.00000000000000    0.00000000000000    0.00000000000000
O   1.95250000000000    1.95250000000000    0.00000000000000
Ru  1.95250000000000    1.95250000000000    1.95250000000000
O   0.00000000000000    1.95250000000000    1.95250000000000
O   1.95250000000000    0.00000000000000    1.95250000000000
Sr  0.00000000000000    0.00000000000000    3.90500000000000
O   1.95250000000000    1.95250000000000    3.90500000000000
Ru  1.95250000000000    1.95250000000000    5.85750000000000
O   0.00000000000000    1.95250000000000    5.85750000000000
O   1.95250000000000    0.00000000000000    5.85750000000000
Sr  0.00000000000000    0.00000000000000    7.81000000000000
O   1.95250000000000    1.95250000000000    7.81000000000000
Ru  1.95250000000000    1.95250000000000    9.76250000000000
O   0.00000000000000    1.95250000000000    9.76250000000000
O   1.95250000000000    0.00000000000000    9.76250000000000
Pb  0.00000000000000    0.00000000000000    11.7202344916000
O   1.95250000000000    1.95250000000000    12.1688551695000
Ti  1.95250000000000    1.95250000000000    13.9438177707000
O   0.00000000000000    1.95250000000000    14.2579079188000
O   1.95250000000000    0.00000000000000    14.2579079188000
Pb  0.00000000000000    0.00000000000000    15.8398546661000
O   1.95250000000000    1.95250000000000    16.2884753441000
Ti  1.95250000000000    1.95250000000000    18.0634379452000
O   0.00000000000000    1.95250000000000    18.3775280934000
O   1.95250000000000    0.00000000000000    18.3775280934000
Pb  0.00000000000000    0.00000000000000    19.9594748407000
O   1.95250000000000    1.95250000000000    20.4080955187000
Ti  1.95250000000000    1.95250000000000    22.1830581198000
O   0.00000000000000    1.95250000000000    22.4971482679000
O   1.95250000000000    0.00000000000000    22.4971482679000
Pb  0.00000000000000    0.00000000000000    24.0790950152000
O   1.95250000000000    1.95250000000000    24.5277156932000
Ti  1.95250000000000    1.95250000000000    26.3026782943000
O   0.00000000000000    1.95250000000000    26.6167684425000
O   1.95250000000000    0.00000000000000    26.6167684425000
Pb  0.00000000000000    0.00000000000000    28.1987151898000
O   1.95250000000000    1.95250000000000    28.6473358678000
Ti  1.95250000000000    1.95250000000000    30.4222984689000
O   0.00000000000000    1.95250000000000    30.7363886171000
O   1.95250000000000    0.00000000000000    30.7363886171000
Pb  0.00000000000000    0.00000000000000    32.3183353644000
O   1.95250000000000    1.95250000000000    32.7669560423000
Ti  1.95250000000000    1.95250000000000    34.5419186435000
O   0.00000000000000    1.95250000000000    34.8560087916000
O   1.95250000000000    0.00000000000000    34.8560087916000
Pb  0.00000000000000    0.00000000000000    36.4379555389000
O   1.95250000000000    1.95250000000000    36.8865762169000
Ti  1.95250000000000    1.95250000000000    38.6615388180000
O   0.00000000000000    1.95250000000000    38.9756289662000
O   1.95250000000000    0.00000000000000    38.9756289662000
Sr  0.00000000000000    0.00000000000000    40.5523412219000
O   1.95250000000000    1.95250000000000    40.5523412219000
Ti  1.95250000000000    1.95250000000000    42.5048412219000
O   0.00000000000000    1.95250000000000    42.5048412219000
O   1.95250000000000    0.00000000000000    42.5048412219000
Sr  0.00000000000000    0.00000000000000    44.4573412219000
O   1.95250000000000    1.95250000000000    44.4573412219000
Ti  1.95250000000000    1.95250000000000    46.4098412219000
O   0.00000000000000    1.95250000000000    46.4098412219000
O   1.95250000000000    0.00000000000000    46.4098412219000
Sr  0.00000000000000    0.00000000000000    48.3623412219000
O   1.95250000000000    1.95250000000000    48.3623412219000
Ti  1.95250000000000    1.95250000000000    50.3148412219000
O   0.00000000000000    1.95250000000000    50.3148412219000
O   1.95250000000000    0.00000000000000    50.3148412219000
Pb  0.00000000000000    0.00000000000000    52.2725757135000
O   1.95250000000000    1.95250000000000    52.7211963915000
Ti  1.95250000000000    1.95250000000000    54.4961589926000
O   0.00000000000000    1.95250000000000    54.8102491407000
O   1.95250000000000    0.00000000000000    54.8102491407000
Pb  0.00000000000000    0.00000000000000    56.3921958880000
O   1.95250000000000    1.95250000000000    56.8408165660000
Ti  1.95250000000000    1.95250000000000    58.6157791671000
O   0.00000000000000    1.95250000000000    58.9298693153000
O   1.95250000000000    0.00000000000000    58.9298693153000
Pb  0.00000000000000    0.00000000000000    60.5118160626000
O   1.95250000000000    1.95250000000000    60.9604367406000
Ti  1.95250000000000    1.95250000000000    62.7353993417000
O   0.00000000000000    1.95250000000000    63.0494894899000
O   1.95250000000000    0.00000000000000    63.0494894899000
Pb  0.00000000000000    0.00000000000000    64.6314362372000
O   1.95250000000000    1.95250000000000    65.0800569151000
Ti  1.95250000000000    1.95250000000000    66.8550195163000
O   0.00000000000000    1.95250000000000    67.1691096644000
O   1.95250000000000    0.00000000000000    67.1691096644000
Pb  0.00000000000000    0.00000000000000    68.7510564117000
O   1.95250000000000    1.95250000000000    69.1996770897000
Ti  1.95250000000000    1.95250000000000    70.9746396908000
O   0.00000000000000    1.95250000000000    71.2887298390000
O   1.95250000000000    0.00000000000000    71.2887298390000
Pb  0.00000000000000    0.00000000000000    72.8706765863000
O   1.95250000000000    1.95250000000000    73.3192972643000
Ti  1.95250000000000    1.95250000000000    75.0942598654000
O   0.00000000000000    1.95250000000000    75.4083500135000
O   1.95250000000000    0.00000000000000    75.4083500135000
Pb  0.00000000000000    0.00000000000000    76.9902967608000
O   1.95250000000000    1.95250000000000    77.4389174388000
Ti  1.95250000000000    1.95250000000000    79.2138800399000
O   0.00000000000000    1.95250000000000    79.5279701881000
O   1.95250000000000    0.00000000000000    79.5279701881000
Sr  0.00000000000000    0.00000000000000    81.1046824438000
O   1.95250000000000    1.95250000000000    81.1046824438000
Ru  1.95250000000000    1.95250000000000    83.0571824438000
O   0.00000000000000    1.95250000000000    83.0571824438000
O   1.95250000000000    0.00000000000000    83.0571824438000
Sr  0.00000000000000    0.00000000000000    85.0096824438000
O   1.95250000000000    1.95250000000000    85.0096824438000
Ru  1.95250000000000    1.95250000000000    86.9621824438000
O   0.00000000000000    1.95250000000000    86.9621824438000
O   1.95250000000000    0.00000000000000    86.9621824438000
Sr  0.00000000000000    0.00000000000000    88.9146824438000
O   1.95250000000000    1.95250000000000    88.9146824438000
Ru  1.95250000000000    1.95250000000000    90.8671824438000
O   0.00000000000000    1.95250000000000    90.8671824438000
O   1.95250000000000    0.00000000000000    90.8671824438000

K_POINTS {automatic}
  3 3 1 0 0 0

Regards,


Lucian

-- 
*Dr. Lucian Dragos Filip*
National Institute of Materials Physics
Atomistilor str. 405A, PO Box MG. 7
Magurele, 077125
Bucharest, Romania
E-mail: lucian.filip at infim.ro
Website: https://lucianfilip.wordpress.com/
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