A simpler but often effective trick: sometimes at (or after) the first
step your system may be trapped in an unlucky configuration that
prevent convergence of the scf iteration. You can either do as Matteo
says, or try (after inspecting the geometry of the second step to be
sure that your system isn't going bananas) to use the switch
scf_must_converge=.false.
Such switch forces the bfgs step even if the wfc is not fully
converged, and it is sensible only if your wfc is not very far from
convergence and in the initial steps of a 'relax' calculation. If you
are lucky, in a few steps you jump out of your "Bermuda triangle" and
further steps converge in a smoother way.
HTH
Giuseppe
Quoting Coralie Khabbaz <[email protected]>:
Hello Matteo,
Thank you so much for your reply. I didn't understand what do you mean by
initial trust radius? Also, at first my convergence threshold was at 1^-6
but the first scf step didn't converge in 1000 steps. Then, I fixed it at
1^-4 and the first step converged. So do you think I should tighten it? I
didn't try starting a new scf from the new iconic positions because I don't
know how to.
This is my input file:
&CONTROL
calculation = "relax"
forc_conv_thr = 1.00000e-03
max_seconds = 4.32000e+05
nstep = 300
pseudo_dir = "/home/coralee/projects/def-jkopysci/coralee/.pseudopot"
/
&SYSTEM
a = 8.32716e+00
angle1(1) = 0.00000e+00
angle1(2) = 0.00000e+00
angle2(1) = 0.00000e+00
angle2(2) = 0.00000e+00
b = 8.98689e+00
c = 2.52767e+01
cosab = 6.12323e-17
cosac = 6.12323e-17
cosbc = -1.85547e-01
degauss = 2.00000e-02
ecutrho = 4.75221e+02
ecutwfc = 5.03902e+01
ibrav = 14
nat = 48
nbnd = 490
nspin = 2
ntyp = 2
occupations = "smearing"
smearing = "gaussian"
starting_magnetization(1) = 2.00000e-01
starting_magnetization(2) = 2.00000e-01
/
&ELECTRONS
conv_thr = 1.00000e-04
diagonalization = "david"
electron_maxstep = 1000
mixing_beta = 1.00000e-01
mixing_mode = "local-TF"
startingpot = "atomic"
startingwfc = "atomic+random"
/
&IONS
ion_dynamics = "bfgs"
/
&CELL
/
K_POINTS {automatic}
2 2 1 0 0 0
ATOMIC_SPECIES
N 14.00674 N.pbe-n-kjpaw_psl.1.0.0.UPF
W 183.84000 W.pbe-spn-kjpaw_psl.1.0.0.UPF
ATOMIC_POSITIONS {angstrom}
N 3.207882 2.672960 14.837784
N 7.371462 2.672960 14.837784
N 3.207882 -1.820484 14.837784
N 7.371462 -1.820484 14.837784
W 3.207882 4.882815 14.748648
W 7.371462 4.882815 14.748648
W 3.207882 0.389371 14.748648
W 7.371462 0.389371 14.748648
N 1.126093 5.365612 14.468179
N 5.289672 5.365612 14.468179
N 1.126093 0.872168 14.468179
N 5.289672 0.872168 14.468179
W 1.126093 3.038143 14.415413
W 5.289672 3.038143 14.415413
W 1.126093 -1.455301 14.415413
W 5.289672 -1.455301 14.415413
N 3.207882 5.336567 12.630078
N 7.371462 5.336567 12.630078
N 3.207882 0.843123 12.630078
N 7.371462 0.843123 12.630078
W 3.207882 3.052977 12.540942
W 7.371462 3.052977 12.540942
W 3.207882 -1.440467 12.540942
W 7.371462 -1.440467 12.540942
N 1.126093 3.535775 12.260473
N 5.289672 3.535775 12.260473
N 1.126093 -0.957669 12.260473
N 5.289672 -0.957669 12.260473
W 1.126093 5.701750 12.207706
W 5.289672 5.701750 12.207706
W 1.126093 1.208305 12.207706
W 5.289672 1.208305 12.207706
N 3.207882 3.506729 10.422372 0 0 0
N 7.371462 3.506729 10.422372 0 0 0
N 3.207882 -0.986715 10.422372 0 0 0
N 7.371462 -0.986715 10.422372 0 0 0
W 3.207882 5.716584 10.333236 0 0 0
W 7.371462 5.716584 10.333236 0 0 0
W 3.207882 1.223140 10.333236 0 0 0
W 7.371462 1.223140 10.333236 0 0 0
N 1.126093 6.199382 10.052766 0 0 0
N 5.289672 6.199382 10.052766 0 0 0
N 1.126093 1.705938 10.052766 0 0 0
N 5.289672 1.705938 10.052766 0 0 0
W 1.126093 3.871912 10.000000 0 0 0
W 5.289672 3.871912 10.000000 0 0 0
W 1.126093 -0.621532 10.000000 0 0 0
W 5.289672 -0.621532 10.000000 0 0 0
On Wed, 1 Jul 2020 at 10:48, Matteo Cococcioni <[email protected]>
wrote:
Hello,
it's very difficult to guess what is wrong in your input if you don't show
it.
In any case, if you have converged forces and stresses on cut-off(s) and
number of k-points/smearing, it might be a good idea to tighten your
convergence threshold and reduce the initial trust radius. Maybe your
forces and stresses are so loosely converged and your ionic/cell step so
big that the system moves to a configuration that is difficult to converge.
Or maybe your starting lattice parameter/ionic configuration are very far
from equilibrium and the system tries to make a big jump at the beginning.
Also, have you tried to start a new scf from the new ionic position?
Please add your affiliation
Regards,
Matteo
Il giorno mer 1 lug 2020 alle ore 13:45 Coralie Khabbaz <
[email protected]> ha scritto:
Hello,
I am doing a relax calculation on my WN (48 atoms) slab. The first step
of scf calculations converged but then the second step didn't converge in
1000 steps (which was my limit). So, the calculations stopped, and I got
many files (data-file.xml, charge-density.dat, paw.txt,
spin-polarization.dat...) but no output file. If my first scf step
converged doesn't that mean that all of my other scf steps should converge
but need more steps? Or is there a problem in my input file?
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--
Matteo Cococcioni
Department of Physics
University of Pavia
Via Bassi 6, I-27100 Pavia, Italy
tel +39-0382-987485
e-mail [email protected] <[email protected]>
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GIUSEPPE MATTIOLI
CNR - ISTITUTO DI STRUTTURA DELLA MATERIA
Via Salaria Km 29,300 - C.P. 10
I-00015 - Monterotondo Scalo (RM)
Mob (*preferred*) +39 373 7305625
Tel + 39 06 90672342 - Fax +39 06 90672316
E-mail: <[email protected]>
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