<p>
Hello <span style="white-space:normal;">Khabbaz,</span>
</p>
<blockquote style="margin:0 0 0 40px;border:none;padding:0px;">
<p>
As I am just a beginner of QE, I can only share my limited, personal experience with you. Note that convergence is a quite general problem that maybe everyone will confront with, I recommend you to look up QE-forum: <a href="https://www.mail-archive.com/users@lists.quantum-espresso.org/">https://www.mail-archive.com/users@lists.quantum-espresso.org/</a>.
</p>
<p>
1. spin-polarized calculation is not easy to converge as non-polarized ones, so if your structure is just built without any primary optimization, I suggest you perform non-polarized optimization first, although it may be of little help on improving convergence.
</p>
<p>
2. you can try different mixing_mode. In general, as suggested in QE forum, local-TF may work well for heterogeneous system, but that is not always true. Sometimes plain mode (also known as Broyden mixing) works better than local-TF. Also, the higher vacuum region you add, the harder will your system to converge.
</p>
<p>
3. you can also try different smearing, although gaussian smearing is default and may be the first recommended, sometimes fd smearing can help your system converge faster, but that all depends.
</p>
<p>
4. you may want to decrease mixing_beta, or modify mixing_dim, to tune the updating rate of density matrix.
</p>
<p>
5. set diagonalization = 'cg' will be of help but will be slower than Davidson.
</p>
<p>
6. note that your system has N element. I remember there was a discussion about one certain (old) kind of nitrogen pseudopotential cause convergence failure, maybe you can test different kinds of pseudopotential.
</p>
</blockquote>
<p>
<br>
</p>
<p>
Best regards!
</p>
<p>
</p>
<p>
Yike Huang, PhD candidate.
</p>
<p>
Dalian Institute of Chemical Physics, CAS, China.
</p>
<p>
<br>
</p>
<blockquote name="replyContent" class="ReferenceQuote" style="padding-left:5px;margin-left:5px;border-left:#b6b6b6 2px solid;margin-right:0;">
-----原始邮件-----<br>
<b>发件人:</b><span id="rc_from">"Coralie Khabbaz" <khabbaz.coralie@gmail.com></span><br>
<b>发送时间:</b><span id="rc_senttime">2020-06-13 01:13:33 (星期六)</span><br>
<b>收件人:</b> users@lists.quantum-espresso.org<br>
<b>抄送:</b> <br>
<b>主题:</b> [QE-users] SCF calculation with no convergence<br>
<br>
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<div dir="ltr">
Hello,
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<br>
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<div>
I am doing an scf calculation on a tungsten nitride (WN) slab (catalyst), with a methane molecule 5 Angstrom away from the surface. The energy values are not converging, even after 533 iterations. The energy values are very negative, and then they increase to a positive value then decrease a lot again. Before building the supercell, I had a WN unit cell with 433 K-points. Then, I built the super cell by using a scaling of 333 and miller indices of 100. I tried using K points of 111 and 222 for my super cell, but the calculations didn't converge for both.
</div>
<div>
<br>
</div>
<div>
This is the input file I am using:
</div>
<div>
<div>
<br>
</div>
<div>
&CONTROL
</div>
<div>
calculation = "scf"
</div>
<div>
max_seconds = 1.72800e+05
</div>
<div>
pseudo_dir = "/home/coralee/projects/def-jkopysci/coralee/.pseudopot"
</div>
<div>
restart_mode = "from_scratch"
</div>
<div>
/
</div>
<div>
<br>
</div>
<div>
&SYSTEM
</div>
<div>
a = 1.24907e+01
</div>
<div>
angle1(1) = 0.00000e+00
</div>
<div>
angle1(2) = 0.00000e+00
</div>
<div>
angle2(1) = 0.00000e+00
</div>
<div>
angle2(2) = 0.00000e+00
</div>
<div>
b = 1.34803e+01
</div>
<div>
c = 2.52767e+01
</div>
<div>
cosab = 6.12323e-17
</div>
<div>
cosac = 6.12323e-17
</div>
<div>
cosbc = -1.85547e-01
</div>
<div>
degauss = 1.00000e-02
</div>
<div>
ecutrho = 2.70000e+02
</div>
<div>
ecutwfc = 3.00000e+01
</div>
<div>
ibrav = 14
</div>
<div>
nat = 113
</div>
<div>
nspin = 2
</div>
<div>
ntyp = 4
</div>
<div>
occupations = "smearing"
</div>
<div>
smearing = "gaussian"
</div>
<div>
starting_magnetization(1) = 2.00000e-01
</div>
<div>
starting_magnetization(2) = 6.00000e-01
</div>
<div>
starting_magnetization(3) = 0.00000e+00
</div>
<div>
starting_magnetization(4) = 0.00000e+00
</div>
<div>
/
</div>
<div>
<br>
</div>
<div>
&ELECTRONS
</div>
<div>
conv_thr = 1.00000e-06
</div>
<div>
diagonalization = "david"
</div>
<div>
electron_maxstep = 528
</div>
<div>
mixing_beta = 4.00000e-01
</div>
<div>
startingpot = "atomic"
</div>
<div>
startingwfc = "atomic+random"
</div>
<div>
/
</div>
<div>
<br>
</div>
<div>
K_POINTS {automatic}
</div>
<div>
2 2 2 0 0 0
</div>
<div>
<br>
</div>
<div>
ATOMIC_SPECIES
</div>
<div>
N 14.00674 N.pbe-n-rrkjus_psl.1.0.0.UPF
</div>
<div>
W 183.84000 W.pbe-spn-rrkjus_psl.1.0.0.UPF
</div>
<div>
C 12.01070 C.pbe-n-rrkjus_psl.1.0.0.UPF
</div>
<div>
H 1.00794 H.pbe-rrkjus_psl.1.0.0.UPF
</div>
<div>
<br>
</div>
<div>
ATOMIC_POSITIONS {angstrom}
</div>
<div>
N 2.481849 0.418242 14.837784
</div>
<div>
N 6.645429 0.418242 14.837784
</div>
<div>
N 10.809008 0.418242 14.837784
</div>
<div>
N 2.481849 4.911686 14.837784
</div>
<div>
N 6.645429 4.911686 14.837784
</div>
<div>
N 10.809008 4.911686 14.837784
</div>
<div>
N 2.481849 9.405131 14.837784
</div>
<div>
N 6.645429 9.405131 14.837784
</div>
<div>
N 10.809008 9.405131 14.837784
</div>
<div>
W 2.481849 2.628097 14.748648
</div>
<div>
W 6.645429 2.628097 14.748648
</div>
<div>
W 10.809008 2.628097 14.748648
</div>
<div>
W 2.481849 7.121541 14.748648
</div>
<div>
W 6.645429 7.121541 14.748648
</div>
<div>
W 10.809008 7.121541 14.748648
</div>
<div>
W 2.481849 -1.865347 14.748648
</div>
<div>
W 6.645429 -1.865347 14.748648
</div>
<div>
W 10.809008 -1.865347 14.748648
</div>
<div>
N 0.400059 3.110895 14.468179
</div>
<div>
N 4.563639 3.110895 14.468179
</div>
<div>
N 8.727218 3.110895 14.468179
</div>
<div>
N 0.400059 7.604339 14.468179
</div>
<div>
N 4.563639 7.604339 14.468179
</div>
<div>
N 8.727218 7.604339 14.468179
</div>
<div>
N 0.400059 -1.382549 14.468179
</div>
<div>
N 4.563639 -1.382549 14.468179
</div>
<div>
N 8.727218 -1.382549 14.468179
</div>
<div>
W 0.400059 0.783425 14.415413
</div>
<div>
W 4.563639 0.783425 14.415413
</div>
<div>
W 8.727218 0.783425 14.415413
</div>
<div>
W 0.400059 5.276869 14.415413
</div>
<div>
W 4.563639 5.276869 14.415413
</div>
<div>
W 8.727218 5.276869 14.415413
</div>
<div>
W 0.400059 9.770314 14.415413
</div>
<div>
W 4.563639 9.770314 14.415413
</div>
<div>
W 8.727218 9.770314 14.415413
</div>
<div>
N 2.481849 3.081849 12.630078 0 0 0
</div>
<div>
N 6.645429 3.081849 12.630078 0 0 0
</div>
<div>
N 10.809008 3.081849 12.630078 0 0 0
</div>
<div>
N 2.481849 7.575293 12.630078 0 0 0
</div>
<div>
N 6.645429 7.575293 12.630078 0 0 0
</div>
<div>
N 10.809008 7.575293 12.630078 0 0 0
</div>
<div>
N 2.481849 -1.411595 12.630078 0 0 0
</div>
<div>
N 6.645429 -1.411595 12.630078 0 0 0
</div>
<div>
N 10.809008 -1.411595 12.630078 0 0 0
</div>
<div>
W 2.481849 0.798260 12.540942 0 0 0
</div>
<div>
W 6.645429 0.798260 12.540942 0 0 0
</div>
<div>
W 10.809008 0.798260 12.540942 0 0 0
</div>
<div>
W 2.481849 5.291704 12.540942 0 0 0
</div>
<div>
W 6.645429 5.291704 12.540942 0 0 0
</div>
<div>
W 10.809008 5.291704 12.540942 0 0 0
</div>
<div>
W 2.481849 9.785148 12.540942 0 0 0
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<div>
W 6.645429 9.785148 12.540942 0 0 0
</div>
<div>
W 10.809008 9.785148 12.540942 0 0 0
</div>
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N 0.400059 1.281057 12.260473 0 0 0
</div>
<div>
N 4.563639 1.281057 12.260473 0 0 0
</div>
<div>
N 8.727218 1.281057 12.260473 0 0 0
</div>
<div>
N 0.400059 5.774502 12.260473 0 0 0
</div>
<div>
N 4.563639 5.774502 12.260473 0 0 0
</div>
<div>
N 8.727218 5.774502 12.260473 0 0 0
</div>
<div>
N 0.400059 10.267946 12.260473 0 0 0
</div>
<div>
N 4.563639 10.267946 12.260473 0 0 0
</div>
<div>
N 8.727218 10.267946 12.260473 0 0 0
</div>
<div>
W 0.400059 3.447032 12.207706 0 0 0
</div>
<div>
W 4.563639 3.447032 12.207706 0 0 0
</div>
<div>
W 8.727218 3.447032 12.207706 0 0 0
</div>
<div>
W 0.400059 7.940476 12.207706 0 0 0
</div>
<div>
W 4.563639 7.940476 12.207706 0 0 0
</div>
<div>
W 8.727218 7.940476 12.207706 0 0 0
</div>
<div>
W 0.400059 -1.046412 12.207706 0 0 0
</div>
<div>
W 4.563639 -1.046412 12.207706 0 0 0
</div>
<div>
W 8.727218 -1.046412 12.207706 0 0 0
</div>
<div>
N 2.481849 1.252012 10.422372 0 0 0
</div>
<div>
N 6.645429 1.252012 10.422372 0 0 0
</div>
<div>
N 10.809008 1.252012 10.422372 0 0 0
</div>
<div>
N 2.481849 5.745456 10.422372 0 0 0
</div>
<div>
N 6.645429 5.745456 10.422372 0 0 0
</div>
<div>
N 10.809008 5.745456 10.422372 0 0 0
</div>
<div>
N 2.481849 10.238900 10.422372 0 0 0
</div>
<div>
N 6.645429 10.238900 10.422372 0 0 0
</div>
<div>
N 10.809008 10.238900 10.422372 0 0 0
</div>
<div>
W 2.481849 3.461867 10.333236 0 0 0
</div>
<div>
W 6.645429 3.461867 10.333236 0 0 0
</div>
<div>
W 10.809008 3.461867 10.333236 0 0 0
</div>
<div>
W 2.481849 7.955311 10.333236 0 0 0
</div>
<div>
W 6.645429 7.955311 10.333236 0 0 0
</div>
<div>
W 10.809008 7.955311 10.333236 0 0 0
</div>
<div>
W 2.481849 -1.031577 10.333236 0 0 0
</div>
<div>
W 6.645429 -1.031577 10.333236 0 0 0
</div>
<div>
W 10.809008 -1.031577 10.333236 0 0 0
</div>
<div>
N 0.400059 3.944664 10.052766 0 0 0
</div>
<div>
N 4.563639 3.944664 10.052766 0 0 0
</div>
<div>
N 8.727218 3.944664 10.052766 0 0 0
</div>
<div>
N 0.400059 8.438108 10.052766 0 0 0
</div>
<div>
N 4.563639 8.438108 10.052766 0 0 0
</div>
<div>
N 8.727218 8.438108 10.052766 0 0 0
</div>
<div>
N 0.400059 -0.548780 10.052766 0 0 0
</div>
<div>
N 4.563639 -0.548780 10.052766 0 0 0
</div>
<div>
N 8.727218 -0.548780 10.052766 0 0 0
</div>
<div>
W 0.400059 1.617195 10.000000 0 0 0
</div>
<div>
W 4.563639 1.617195 10.000000 0 0 0
</div>
<div>
W 8.727218 1.617195 10.000000 0 0 0
</div>
<div>
W 0.400059 6.110639 10.000000 0 0 0
</div>
<div>
W 4.563639 6.110639 10.000000 0 0 0
</div>
<div>
W 8.727218 6.110639 10.000000 0 0 0
</div>
<div>
W 0.400059 10.604083 10.000000 0 0 0
</div>
<div>
W 4.563639 10.604083 10.000000 0 0 0
</div>
<div>
W 8.727218 10.604083 10.000000 0 0 0
</div>
<div>
C 10.809008 2.628097 19.750000
</div>
<div>
H 10.177000 1.997000 20.383000
</div>
<div>
H 11.443000 1.997000 19.117000
</div>
<div>
H 10.177000 3.263000 19.117000
</div>
<div>
H 11.443000 3.263000 20.383000
</div>
<div>
<br>
</div>
<div>
<br>
</div>
</div>
</div>
</div>
</blockquote>
<br>
<br>
<br>