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I am a sort-of-beginner in Quantum Espresso. I do understand certain terminology in the INPUT file but I am faced with a dilemma. I have been trying to optimize $\ce{Fe}(110)$ system of 100 atoms using the relax keyword. I would like to know if my input file has any mistakes, as I am not able to achieve convergence even after a 1000 iterations.

Below, I have added the INPUT and OUTPUT files.

I realize that the Total Energy is very different at every iteration, but is it supposed to be like that after 1000 iterations. Any help or advice would be much appreciated.

INPUT

&CONTROL
calculation   = "relax"
forc_conv_thr =  1.00000e-03
max_seconds   =  1.72800e+05
nstep         = 201
pseudo_dir    = "C:\Users\ECR2017-001147-SYS-2\.burai\.pseudopot"
/
&SYSTEM
a                         =  2.02685e+01
angle1(1)                 =  0.00000e+00
angle2(1)                 =  0.00000e+00
b                         =  1.43320e+01
c                         =  3.02685e+01
degauss                   =  2.00000e-02
ecutrho                   =  3.00000e+02
ecutwfc                   =  3.00000e+01
ibrav                     = 9
nat                       = 100
nspin                     = 1
ntyp                      = 1
occupations               = "smearing"
smearing                  = "marzari-vanderbilt"
starting_magnetization(1) =  0.00000e+00
/
&ELECTRONS
conv_thr         =  1.00000e-06
electron_maxstep = 1000
mixing_beta      =  4.00000e-01
startingpot      = "atomic"
startingwfc      = "atomic+random"
/
&IONS
ion_dynamics = "bfgs"
/
&CELL
/
K_POINTS {gamma}
ATOMIC_SPECIES
Fe     55.84500  Fe.pbe-n-rrkjus_psl.1.0.0.UPF

ATOMIC_POSITIONS {angstrom}
Fe      0.000000   0.000000  22.161105
Fe      0.000000   0.000000  26.214807  0 0 0
Fe     -2.026851   1.433200  22.161105
Fe     -2.026851   1.433200  26.214807  0 0 0
Fe     -4.053702   2.866400  22.161105
Fe     -4.053702   2.866400  26.214807  0 0 0
Fe     -6.080553   4.299600  22.161105
Fe     -6.080553   4.299600  26.214807  0 0 0
Fe     -8.107403   5.732800  22.161105
Fe     -8.107403   5.732800  26.214807  0 0 0
Fe      2.026851   1.433200  22.161105
Fe      2.026851   1.433200  26.214807  0 0 0
Fe      0.000000   2.866400  22.161105
Fe      0.000000   2.866400  26.214807  0 0 0
Fe     -2.026851   4.299600  22.161105
Fe     -2.026851   4.299600  26.214807  0 0 0
Fe     -4.053702   5.732800  22.161105
Fe     -4.053702   5.732800  26.214807  0 0 0
Fe     -6.080553   7.166000  22.161105
Fe     -6.080553   7.166000  26.214807  0 0 0
Fe      4.053702   2.866400  22.161105
Fe      4.053702   2.866400  26.214807  0 0 0
Fe      2.026851   4.299600  22.161105
Fe      2.026851   4.299600  26.214807  0 0 0
Fe      0.000000   5.732800  22.161105
Fe      0.000000   5.732800  26.214807  0 0 0
Fe     -2.026851   7.166000  22.161105
Fe     -2.026851   7.166000  26.214807  0 0 0
Fe     -4.053702   8.599200  22.161105
Fe     -4.053702   8.599200  26.214807  0 0 0
Fe      6.080553   4.299600  22.161105
Fe      6.080553   4.299600  26.214807  0 0 0
Fe      4.053702   5.732800  22.161105
Fe      4.053702   5.732800  26.214807  0 0 0
Fe      2.026851   7.166000  22.161105
Fe      2.026851   7.166000  26.214807  0 0 0
Fe      0.000000   8.599200  22.161105
Fe      0.000000   8.599200  26.214807  0 0 0
Fe     -2.026851  10.032400  22.161105
Fe     -2.026851  10.032400  26.214807  0 0 0
Fe      8.107403   5.732800  22.161105
Fe      8.107403   5.732800  26.214807  0 0 0
Fe      6.080553   7.166000  22.161105
Fe      6.080553   7.166000  26.214807  0 0 0
Fe      4.053702   8.599200  22.161105
Fe      4.053702   8.599200  26.214807  0 0 0
Fe      2.026851  10.032400  22.161105
Fe      2.026851  10.032400  26.214807  0 0 0
Fe      0.000000  11.465600  22.161105
Fe      0.000000  11.465600  26.214807  0 0 0
Fe      0.000000   1.433200  24.187956
Fe      0.000000   1.433200  28.241658  0 0 0
Fe     -2.026851   2.866400  24.187956
Fe     -2.026851   2.866400  28.241658  0 0 0
Fe     -4.053702   4.299600  24.187956
Fe     -4.053702   4.299600  28.241658  0 0 0
Fe     -6.080553   5.732800  24.187956
Fe     -6.080553   5.732800  28.241658  0 0 0
Fe     -8.107403   7.166000  24.187956
Fe     -8.107403   7.166000  28.241658  0 0 0
Fe      2.026851   2.866400  24.187956
Fe      2.026851   2.866400  28.241658  0 0 0
Fe      0.000000   4.299600  24.187956
Fe      0.000000   4.299600  28.241658  0 0 0
Fe     -2.026851   5.732800  24.187956
Fe     -2.026851   5.732800  28.241658  0 0 0
Fe     -4.053702   7.166000  24.187956
Fe     -4.053702   7.166000  28.241658  0 0 0
Fe     -6.080553   8.599200  24.187956
Fe     -6.080553   8.599200  28.241658  0 0 0
Fe      4.053702   4.299600  24.187956
Fe      4.053702   4.299600  28.241658  0 0 0
Fe      2.026851   5.732800  24.187956
Fe      2.026851   5.732800  28.241658  0 0 0
Fe      0.000000   7.166000  24.187956
Fe      0.000000   7.166000  28.241658  0 0 0
Fe     -2.026851   8.599200  24.187956
Fe     -2.026851   8.599200  28.241658  0 0 0
Fe     -4.053702  10.032400  24.187956
Fe     -4.053702  10.032400  28.241658  0 0 0
Fe      6.080553   5.732800  24.187956
Fe      6.080553   5.732800  28.241658  0 0 0
Fe      4.053702   7.166000  24.187956
Fe      4.053702   7.166000  28.241658  0 0 0
Fe      2.026851   8.599200  24.187956
Fe      2.026851   8.599200  28.241658  0 0 0
Fe      0.000000  10.032400  24.187956
Fe      0.000000  10.032400  28.241658  0 0 0
Fe     -2.026851  11.465600  24.187956
Fe     -2.026851  11.465600  28.241658  0 0 0
Fe      8.107403   7.166000  24.187956
Fe      8.107403   7.166000  28.241658  0 0 0
Fe      6.080553   8.599200  24.187956
Fe      6.080553   8.599200  28.241658  0 0 0
Fe      4.053702  10.032400  24.187956
Fe      4.053702  10.032400  28.241658  0 0 0
Fe      2.026851  11.465600  24.187956
Fe      2.026851  11.465600  28.241658  0 0 0
Fe      0.000000  12.898800  24.187956
Fe      0.000000  12.898800  28.241658  0 0 0

OUTPUT

 iteration #997     ecut=    30.00 Ry     beta= 0.40
 Davidson diagonalization with overlap
 ethr =  1.00E-02,  avg # of iterations = 12.0

 negative rho (up, down):  1.395E-02 0.000E+00

 total cpu time spent up to now is    22170.2 secs

 total energy              =   -5973.86651878 Ry
 estimated scf accuracy    <    5458.14010799 Ry

 iteration #998     ecut=    30.00 Ry     beta= 0.40
 Davidson diagonalization with overlap
 ethr =  1.00E-02,  avg # of iterations = 10.0

 negative rho (up, down):  1.534E-02 0.000E+00

 total cpu time spent up to now is    22192.6 secs

 total energy              =   -5974.20572642 Ry
 estimated scf accuracy    <    5314.30707048 Ry

 iteration #999     ecut=    30.00 Ry     beta= 0.40
 Davidson diagonalization with overlap
 ethr =  1.00E-02,  avg # of iterations = 11.0

 negative rho (up, down):  1.396E-02 0.000E+00

 total cpu time spent up to now is    22216.5 secs

 total energy              =   -5975.49792049 Ry
 estimated scf accuracy    <    5150.12853865 Ry

 iteration #***     ecut=    30.00 Ry     beta= 0.40
 Davidson diagonalization with overlap
 ethr =  1.00E-02,  avg # of iterations = 10.0

 negative rho (up, down):  1.289E-02 0.000E+00

 total cpu time spent up to now is    22239.0 secs

 total energy              =   -5926.34136165 Ry
 estimated scf accuracy    <    6965.42552475 Ry

 End of self-consistent calculation

 convergence NOT achieved after *** iterations: stopping

 Writing config to output data dir ./pwscf.save/
 Message from routine punch:
 wavefunctions written to file

 init_run     :      6.72s CPU      7.14s WALL (       1 calls)
 electrons    :  21312.84s CPU  22231.70s WALL (       1 calls)

 Called by init_run:
 wfcinit      :      3.38s CPU      3.61s WALL (       1 calls)
 potinit      :      1.01s CPU      1.05s WALL (       1 calls)
 hinit0       :      1.33s CPU      1.37s WALL (       1 calls)

 Called by electrons:
 c_bands      :  19475.35s CPU  20150.60s WALL (    1000 calls)
 sum_band     :   1204.55s CPU   1345.18s WALL (    1000 calls)
 v_of_rho     :    219.62s CPU    234.73s WALL (    1001 calls)
 newd         :    342.84s CPU    427.16s WALL (    1001 calls)
 mix_rho      :     44.44s CPU     46.55s WALL (    1000 calls)

 Called by c_bands:
 init_us_2    :     65.20s CPU     65.53s WALL (    2001 calls)
 init_us_2:cp :     65.18s CPU     65.52s WALL (    2001 calls)
 regterg      :  19356.44s CPU  20031.09s WALL (    1000 calls)

 Called by *egterg:
 rdiaghg      :   4324.36s CPU   4337.94s WALL (   11588 calls)
 h_psi        :   9622.94s CPU  10165.80s WALL (   11589 calls)
 s_psi        :   1153.42s CPU   1157.94s WALL (   11589 calls)
 g_psi        :     37.50s CPU     37.78s WALL (   10588 calls)

 Called by h_psi:
 h_psi:calbec :   1276.51s CPU   1321.47s WALL (   11589 calls)
 vloc_psi     :   7109.30s CPU   7597.77s WALL (   11589 calls)
 add_vuspsi   :   1148.67s CPU   1157.60s WALL (   11589 calls)

 General routines
 calbec       :   1422.99s CPU   1473.42s WALL (   12589 calls)
 fft          :    133.28s CPU    146.87s WALL (   11011 calls)
 ffts         :      4.20s CPU      4.74s WALL (    2001 calls)
 fftw         :   4916.73s CPU   5316.44s WALL ( 4112726 calls)
 interpolate  :     15.78s CPU     17.07s WALL (    1001 calls)
 davcio       :      0.01s CPU      0.22s WALL (      19 calls)



  Parallel routines

     PWSCF        :      5h55m CPU      6h10m WALL


   This run was terminated on:  22:47:47  11May2022            

=------------------------------------------------------------------------------=
   JOB DONE.
=------------------------------------------------------------------------------=
$\endgroup$
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  • $\begingroup$ I have few questions, why slab consists of only four layer, why you think there will be adjustment only to first two layer. Why initial magnetization is 0 for iron. did you have done same for smaller unit cell relaxation. why you want angle1 and angle2 to be zero. you can do collinear spin calculation. $\endgroup$ Commented May 12, 2022 at 17:32
  • $\begingroup$ Thanks everyone for the help. After quite a while, I got the Fe slab to converge. I achieved this after increasing the ecutwfc and ecutrho to 90 and 1080Ry respectively while also introducing 'cg' diagonalization. It took a day to converge with promising results. Thank you Amir K for your suggestions. Cheers! $\endgroup$
    – DevxAtom
    Commented Jul 20, 2022 at 5:40

1 Answer 1

2
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You could try to relax a (much smaller) unit cell for iron, then after that is relaxed you can create and relax the slab with initial guess as the already pre-relaxed coordinates for the irons, which should be much easier. In case it is needed - you can find a tutorial on how to get the slab from the unit cell using VESTA in this link.

In any case, if it continues like this you should ask for larger convergence thresholds - both for energy and for the forces, and only after it converges for these larger values then you begin tightening them.

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2
  • $\begingroup$ Thank you, Maxim, for your reply. Based on your suggestion, would it be right if I optimize a unit cell (i.e. optimization of KE cutoff, charge density cutoff and K_POINTS) and take those values to a supercell? Or would I have to do "relax" optimization again on the supercell?Is it logically correct, if I only optimize the unit cell, make a supercell and carry out further studies? $\endgroup$
    – DevxAtom
    Commented Jun 3, 2022 at 6:18
  • $\begingroup$ It depends on what you are looking for. When you create the slab from a relaxed unit cell you get a "pristine" slab. If you relax the slab you can get reconstruction phenomena which can either gain physics or lose them depending on your system. In my systems the reconstruction is not physical so I don't relax the supercell, but in other systems it might be. $\endgroup$
    – Amir K
    Commented Jun 4, 2022 at 11:06

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