peculiar geometry convergence problem

[SKM]

Hi all

what is happening in this convergence is not sure. a super cell slab with vacuum and Hydrogen Iodide on top is trying for convergence.
i tried different tags by changing values of ISMEAR, IBRION, IALGO, or ALGO etc. but not converging. Now, with this following input
INCAR:
PREC = Normal
NPAR=4
IBRION = 1
ISIF = 2
ENCUT = 450
EDIFF = 1.0e-05
EDIFFG = 1e-04
IVDW = 11
ISMEAR = 0; SIGMA = 0.02
ALGO = Fast
LREAL = Auto
LWAVE = .FALSE.
LCHARG = .FALSE.
ADDGRID = .TRUE.
ISYM = 2
SYMPREC = 1e-05
AMIX = 0.01
NSW=500


POSCAR
POSCAR-system-HI-vac
1.0
4.0149998665 0.0000000000 0.0000000000
0.0000000000 4.0149998665 0.0000000000
0.0000000000 0.0000000000 80.0000000000
Bi I O H
10 13 10 1
Selective Dynamics
Direct
-0.000000000 0.500000000 0.073670000 F F F
0.500000000 -0.000000000 0.104570007 F F F
0.000000000 0.500000000 0.188870001 T T T
0.500000000 0.000000000 0.219740009 T T T
0.000000000 0.500000000 0.304460001 T T T
0.500000000 -0.000000000 0.335350013 T T T
0.000000000 0.500000000 0.420170021 T T T
0.500000000 -0.000000000 0.451049995 T T T
0.000000000 0.500000000 0.536769962 T T T
0.500000000 0.000000000 0.567679977 T T T
0.500000000 0.000000000 0.050519997 F F F
0.000000000 0.500000000 0.011409999 F F F
0.500000000 -0.000000000 0.165930009 T T T
-0.000000000 0.500000000 0.127560008 T T T
0.500000000 -0.000000000 0.281459999 T T T
0.000000000 0.500000000 0.242750001 T T T
0.500000000 0.000000000 0.397170019 T T T
0.000000000 0.500000000 0.358379984 T T T
0.500000000 -0.000000000 0.513649988 T T T
-0.000000000 0.500000000 0.474130011 T T T
0.500000000 -0.000000000 0.630259991 T T T
0.000000000 0.500000000 0.590889978 T T T
0.516579979 0.687180028 0.645969963 T T T
0.000000000 0.000000000 0.089129996 F F F
0.500000000 0.500000000 0.089129996 F F F
0.000000000 0.000000000 0.204309988 T T T
0.500000000 0.500000000 0.204309988 T T T
-0.000000000 -0.000000000 0.319910002 T T T
0.500000000 0.500000000 0.319910002 T T T
-0.000000000 -0.000000000 0.435610008 T T T
0.500000000 0.500000000 0.435610008 T T T
0.000000000 0.000000000 0.552219963 T T T
0.500000000 0.500000000 0.552219963 T T T
0.531970003 0.280240058 0.646049976 T T T

the summary output for each ionic step is as below

1 Energy: 1449.990439 Log|dE|: 3.161 SCF: 60 Avg|F|: 12.527 Max|F|: 39.456 Vol.: 1289.6 Time: 13.06m
2 Energy: -11471.530369 Log|dE|: 4.111 SCF: 60 Avg|F|: 33.227 Max|F|: 96.104 Vol.: 1289.6 Time: 12.80m
3 Energy: 8083.102103 Log|dE|: 4.291 SCF: 60 Avg|F|: 82.133 Max|F|: 246.486 Vol.: 1289.6 Time: 12.45m
4 Energy: -363806.732590 Log|dE|: 5.570 SCF: 60 Avg|F|: 1421.027 Max|F|: 3217.849 Vol.: 1289.6 Time: 12.39m
5 Energy: -237203.595882 Log|dE|: 5.102 SCF: 60 Avg|F|: 1011.686 Max|F|: 2389.491 Vol.: 1289.6 Time: 12.28m

absolutely strange.

Can anyone, through light on whats wrong with input tags, or any issue with the Atoms, like Bi and Iodine?

[martin.schlipf]

At a first glance it looks like your electronic self consistency did not converge.

[SKM]

hi Admin
thank you.
i understand the electronic SCF not converged. Whereas, i knew most of the times, subsequent steps of electronic convergence happens after the 1st,2nd, or 3rd steps, or sometimes, more are not converged. So, some times, left it run and i finally get ionic convergence.

Having said that, if i increase NELM > 60 (default?) i.e. say 200 or some times even 800 i used to give, and rarely some systems used to converged at very high NELM values.

My point and query is any specific reasons for a system to behave like this or can we keep looking for any specific tags to put under test for such systems?

Regards

[martin.schlipf]

If your electronic SCF does not converge it can be very damaging to your ionic relaxation. Keep in mind that the ionic optimizer assumes that your results are converged, but if the forces are drastically different it may lead you down a bad path. Therefore in general it is a good idea to stop a calculation and restart from the obtained structure. That being said of course there may be special cases where the forces are still somewhat reasonable so that losing the history is not a good idea.

As for how to achieve the electronic self consistency, there are a couple of tricks you can employ:
* Just increasing NELM may do the trick when close to convergence
* Change to a different ALGO (All, Normal, Fast)
* Increase NBANDS in particular for magnetic systems and/or f-electron systems
* Tweak the mixing parameters (AMIX, BMIX, AMIN, ...), the Wiki gives some suggestions as to when this is appropriate.

[SKM]

Therefore in general it is a good idea to stop a calculation and restart from the obtained structure. That being said of course there may be special cases where the forces are still somewhat reasonable so that losing the history is not a good idea.

1. i am not clear about your saying "..restart from the obtained structure..". What is this "obtained structure"? from original or you mean the structure obtained just before where the electronic convergence not happened?
2. what do you mean "..losing the history is not a good idea"?

3. Also see below this strange ionic steps summary. the energy keep fluctuating very narrowly but not converging for long time just wasting computing time. (even the electronic convergence happens ionic convergence is not)

------
------
37 Energy: -268.166505 Log|dE|: -1.353 SCF: 13 Avg|F|: 0.081 Max|F|: 0.202 Vol.: 2215.7 Time: 1.00m
38 Energy: -268.021569 Log|dE|: -0.839 SCF: 12 Avg|F|: 0.087 Max|F|: 0.225 Vol.: 2215.7 Time: 0.96m
39 Energy: -268.368348 Log|dE|: -0.460 SCF: 23 Avg|F|: 0.082 Max|F|: 0.222 Vol.: 2215.7 Time: 1.83m
40 Energy: -268.321138 Log|dE|: -1.326 SCF: 10 Avg|F|: 0.081 Max|F|: 0.213 Vol.: 2215.7 Time: 0.78m
41 Energy: -268.196513 Log|dE|: -0.904 SCF: 18 Avg|F|: 0.081 Max|F|: 0.208 Vol.: 2215.7 Time: 1.40m
42 Energy: -268.236007 Log|dE|: -1.403 SCF: 11 Avg|F|: 0.081 Max|F|: 0.202 Vol.: 2215.7 Time: 0.87m
43 Energy: -268.257538 Log|dE|: -1.667 SCF: 4 Avg|F|: 0.082 Max|F|: 0.208 Vol.: 2215.7 Time: 0.31m
44 Energy: -268.022443 Log|dE|: -0.629 SCF: 20 Avg|F|: 0.087 Max|F|: 0.185 Vol.: 2215.7 Time: 1.58m
45 Energy: -268.261808 Log|dE|: -0.621 SCF: 20 Avg|F|: 0.081 Max|F|: 0.200 Vol.: 2215.7 Time: 1.58m
46 Energy: -268.407655 Log|dE|: -0.836 SCF: 19 Avg|F|: 0.080 Max|F|: 0.223 Vol.: 2215.7 Time: 1.48m
47 Energy: -268.204483 Log|dE|: -0.692 SCF: 23 Avg|F|: 0.081 Max|F|: 0.201 Vol.: 2215.7 Time: 1.78m
48 Energy: -268.237378 Log|dE|: -1.483 SCF: 11 Avg|F|: 0.081 Max|F|: 0.195 Vol.: 2215.7 Time: 0.84m
49 Energy: -268.258722 Log|dE|: -1.671 SCF: 4 Avg|F|: 0.082 Max|F|: 0.205 Vol.: 2215.7 Time: 0.31m
50 Energy: -268.108381 Log|dE|: -0.823 SCF: 20 Avg|F|: 0.085 Max|F|: 0.202 Vol.: 2215.7 Time: 1.56m
51 Energy: -268.309051 Log|dE|: -0.698 SCF: 20 Avg|F|: 0.082 Max|F|: 0.206 Vol.: 2215.7 Time: 1.58m
52 Energy: -268.371639 Log|dE|: -1.204 SCF: 12 Avg|F|: 0.082 Max|F|: 0.210 Vol.: 2215.7 Time: 0.94m
53 Energy: -268.283493 Log|dE|: -1.055 SCF: 18 Avg|F|: 0.083 Max|F|: 0.207 Vol.: 2215.7 Time: 1.39m
54 Energy: -268.446572 Log|dE|: -0.788 SCF: 15 Avg|F|: 0.079 Max|F|: 0.198 Vol.: 2215.7 Time: 1.19m
55 Energy: -268.703669 Log|dE|: -0.590 SCF: 23 Avg|F|: 0.085 Max|F|: 0.226 Vol.: 2215.7 Time: 1.80m
56 Energy: -268.247489 Log|dE|: -0.341 SCF: 30 Avg|F|: 0.081 Max|F|: 0.195 Vol.: 2215.7 Time: 2.33m
57 Energy: -268.188313 Log|dE|: -1.228 SCF: 10 Avg|F|: 0.081 Max|F|: 0.197 Vol.: 2215.7 Time: 0.79m
58 Energy: -268.153783 Log|dE|: -1.462 SCF: 11 Avg|F|: 0.081 Max|F|: 0.184 Vol.: 2215.7 Time: 0.85m
59 Energy: -268.133491 Log|dE|: -1.693 SCF: 4 Avg|F|: 0.082 Max|F|: 0.184 Vol.: 2215.7 Time: 0.31m
60 Energy: -268.133107 Log|dE|: -3.416 SCF: 2 Avg|F|: 0.082 Max|F|: 0.186 Vol.: 2215.7 Time: 0.15m
61 Energy: -268.220908 Log|dE|: -1.056 SCF: 18 Avg|F|: 0.082 Max|F|: 0.200 Vol.: 2215.7 Time: 1.38m
62 Energy: -268.057059 Log|dE|: -0.786 SCF: 12 Avg|F|: 0.087 Max|F|: 0.190 Vol.: 2215.7 Time: 0.97m
63 Energy: -268.417844 Log|dE|: -0.443 SCF: 22 Avg|F|: 0.081 Max|F|: 0.224 Vol.: 2215.7 Time: 1.75m
64 Energy: -268.337487 Log|dE|: -1.095 SCF: 11 Avg|F|: 0.082 Max|F|: 0.220 Vol.: 2215.7 Time: 0.87m
65 Energy: -268.381529 Log|dE|: -1.356 SCF: 15 Avg|F|: 0.082 Max|F|: 0.223 Vol.: 2215.7 Time: 1.14m
66 Energy: -268.320035 Log|dE|: -1.211 SCF: 12 Avg|F|: 0.082 Max|F|: 0.213 Vol.: 2215.7 Time: 0.93m
67 Energy: -268.300560 Log|dE|: -1.711 SCF: 4 Avg|F|: 0.083 Max|F|: 0.207 Vol.: 2215.7 Time: 0.31m
68 Energy: -268.321048 Log|dE|: -1.688 SCF: 4 Avg|F|: 0.083 Max|F|: 0.213 Vol.: 2215.7 Time: 0.31m
69 Energy: -268.219967 Log|dE|: -0.995 SCF: 11 Avg|F|: 0.081 Max|F|: 0.188 Vol.: 2215.7 Time: 0.87m
70 Energy: -267.931669 Log|dE|: -0.540 SCF: 20 Avg|F|: 0.090 Max|F|: 0.166 Vol.: 2215.7 Time: 1.59m
71 Energy: -268.287474 Log|dE|: -0.449 SCF: 21 Avg|F|: 0.082 Max|F|: 0.200 Vol.: 2215.7 Time: 1.66m
72 Energy: -268.284415 Log|dE|: -2.514 SCF: 4 Avg|F|: 0.082 Max|F|: 0.200 Vol.: 2215.7 Time: 0.30m
73 Energy: -268.277592 Log|dE|: -2.166 SCF: 4 Avg|F|: 0.082 Max|F|: 0.187 Vol.: 2215.7 Time: 0.31m
74 Energy: -268.274518 Log|dE|: -2.512 SCF: 7 Avg|F|: 0.081 Max|F|: 0.183 Vol.: 2215.7 Time: 0.54m
75 Energy: -268.281873 Log|dE|: -2.133 SCF: 4 Avg|F|: 0.082 Max|F|: 0.188 Vol.: 2215.7 Time: 0.31m
76 Energy: -268.235411 Log|dE|: -1.333 SCF: 15 Avg|F|: 0.081 Max|F|: 0.186 Vol.: 2215.7 Time: 1.15m
77 Energy: -268.238302 Log|dE|: -2.539 SCF: 4 Avg|F|: 0.082 Max|F|: 0.186 Vol.: 2215.7 Time: 0.30m
78 Energy: -268.222327 Log|dE|: -1.797 SCF: 4 Avg|F|: 0.080 Max|F|: 0.185 Vol.: 2215.7 Time: 0.31m
79 Energy: -268.180127 Log|dE|: -1.375 SCF: 16 Avg|F|: 0.085 Max|F|: 0.189 Vol.: 2215.7 Time: 1.22m
80 Energy: -268.271401 Log|dE|: -1.040 SCF: 20 Avg|F|: 0.083 Max|F|: 0.193 Vol.: 2215.7 Time: 1.55m
81 Energy: -268.260469 Log|dE|: -1.961 SCF: 4 Avg|F|: 0.081 Max|F|: 0.181 Vol.: 2215.7 Time: 0.31m
82 Energy: -268.229887 Log|dE|: -1.515 SCF: 12 Avg|F|: 0.082 Max|F|: 0.189 Vol.: 2215.7 Time: 0.95m
83 Energy: -268.256263 Log|dE|: -1.579 SCF: 15 Avg|F|: 0.081 Max|F|: 0.186 Vol.: 2215.7 Time: 1.15m
84 Energy: -268.257172 Log|dE|: -3.041 SCF: 4 Avg|F|: 0.081 Max|F|: 0.187 Vol.: 2215.7 Time: 0.31m
85 Energy: -268.265362 Log|dE|: -2.087 SCF: 4 Avg|F|: 0.082 Max|F|: 0.190 Vol.: 2215.7 Time: 0.31m
86 Energy: -268.165736 Log|dE|: -1.002 SCF: 16 Avg|F|: 0.084 Max|F|: 0.188 Vol.: 2215.7 Time: 1.26m
87 Energy: -268.388885 Log|dE|: -0.651 SCF: 25 Avg|F|: 0.085 Max|F|: 0.195 Vol.: 2215.7 Time: 1.94m
88 Energy: -268.274522 Log|dE|: -0.942 SCF: 15 Avg|F|: 0.084 Max|F|: 0.194 Vol.: 2215.7 Time: 1.20m
89 Energy: -268.306048 Log|dE|: -1.501 SCF: 5 Avg|F|: 0.088 Max|F|: 0.214 Vol.: 2215.7 Time: 0.39m
90 Energy: -268.023725 Log|dE|: -0.549 SCF: 21 Avg|F|: 0.087 Max|F|: 0.182 Vol.: 2215.7 Time: 1.68m
91 Energy: -268.048492 Log|dE|: -1.606 SCF: 4 Avg|F|: 0.087 Max|F|: 0.186 Vol.: 2215.7 Time: 0.31m
92 Energy: -267.974594 Log|dE|: -1.131 SCF: 15 Avg|F|: 0.089 Max|F|: 0.184 Vol.: 2215.7 Time: 1.15m
93 Energy: -268.185362 Log|dE|: -0.676 SCF: 20 Avg|F|: 0.081 Max|F|: 0.178 Vol.: 2215.7 Time: 1.59m
94 Energy: -268.260803 Log|dE|: -1.122 SCF: 17 Avg|F|: 0.081 Max|F|: 0.181 Vol.: 2215.7 Time: 1.31m
95 Energy: -268.306366 Log|dE|: -1.341 SCF: 10 Avg|F|: 0.083 Max|F|: 0.188 Vol.: 2215.7 Time: 0.78m
96 Energy: -268.191572 Log|dE|: -0.940 SCF: 20 Avg|F|: 0.082 Max|F|: 0.181 Vol.: 2215.7 Time: 1.56m
97 Energy: -268.163066 Log|dE|: -1.545 SCF: 11 Avg|F|: 0.081 Max|F|: 0.177 Vol.: 2215.7 Time: 0.84m
98 Energy: -267.975919 Log|dE|: -0.728 SCF: 19 Avg|F|: 0.088 Max|F|: 0.185 Vol.: 2215.7 Time: 1.50m
99 Energy: -268.392059 Log|dE|: -0.381 SCF: 26 Avg|F|: 0.083 Max|F|: 0.197 Vol.: 2215.7 Time: 2.04m
100 Energy: -268.265042 Log|dE|: -0.896 SCF: 22 Avg|F|: 0.082 Max|F|: 0.184 Vol.: 2215.7 Time: 1.71m
101 Energy: -268.107311 Log|dE|: -0.802 SCF: 20 Avg|F|: 0.083 Max|F|: 0.175 Vol.: 2215.7 Time: 1.58m
102 Energy: -268.277815 Log|dE|: -0.768 SCF: 20 Avg|F|: 0.082 Max|F|: 0.183 Vol.: 2215.7 Time: 1.58m
103 Energy: -268.290991 Log|dE|: -1.880 SCF: 4 Avg|F|: 0.083 Max|F|: 0.188 Vol.: 2215.7 Time: 0.31m
104 Energy: -268.075276 Log|dE|: -0.666 SCF: 24 Avg|F|: 0.085 Max|F|: 0.174 Vol.: 2215.7 Time: 1.87m
105 Energy: -268.251566 Log|dE|: -0.754 SCF: 20 Avg|F|: 0.082 Max|F|: 0.180 Vol.: 2215.7 Time: 1.57m
106 Energy: -268.404005 Log|dE|: -0.817 SCF: 20 Avg|F|: 0.084 Max|F|: 0.200 Vol.: 2215.7 Time: 1.57m
107 Energy: -268.037410 Log|dE|: -0.436 SCF: 29 Avg|F|: 0.086 Max|F|: 0.169 Vol.: 2215.7 Time: 2.26m
108 Energy: -268.151849 Log|dE|: -0.941 SCF: 19 Avg|F|: 0.082 Max|F|: 0.175 Vol.: 2215.7 Time: 1.47m
109 Energy: -268.425567 Log|dE|: -0.563 SCF: 20 Avg|F|: 0.082 Max|F|: 0.201 Vol.: 2215.7 Time: 1.59m
110 Energy: -268.289013 Log|dE|: -0.865 SCF: 20 Avg|F|: 0.083 Max|F|: 0.190 Vol.: 2215.7 Time: 1.56m
111 Energy: -268.326931 Log|dE|: -1.421 SCF: 10 Avg|F|: 0.083 Max|F|: 0.192 Vol.: 2215.7 Time: 0.78m
112 Energy: -268.320206 Log|dE|: -2.172 SCF: 4 Avg|F|: 0.081 Max|F|: 0.188 Vol.: 2215.7 Time: 0.31m
113 Energy: -268.128046 Log|dE|: -0.716 SCF: 20 Avg|F|: 0.085 Max|F|: 0.184 Vol.: 2215.7 Time: 1.59m
114 Energy: -268.410125 Log|dE|: -0.550 SCF: 20 Avg|F|: 0.082 Max|F|: 0.199 Vol.: 2215.7 Time: 1.59m
115 Energy: -268.358281 Log|dE|: -1.285 SCF: 12 Avg|F|: 0.083 Max|F|: 0.197 Vol.: 2215.7 Time: 0.94m
116 Energy: -268.356139 Log|dE|: -2.669 SCF: 4 Avg|F|: 0.085 Max|F|: 0.203 Vol.: 2215.7 Time: 0.30m
117 Energy: -268.438906 Log|dE|: -1.082 SCF: 16 Avg|F|: 0.082 Max|F|: 0.201 Vol.: 2215.7 Time: 1.24m
118 Energy: -268.531710 Log|dE|: -1.032 SCF: 18 Avg|F|: 0.084 Max|F|: 0.212 Vol.: 2215.7 Time: 1.39m
119 Energy: -268.329557 Log|dE|: -0.694 SCF: 21 Avg|F|: 0.084 Max|F|: 0.193 Vol.: 2215.7 Time: 1.64m
120 Energy: -268.332690 Log|dE|: -2.504 SCF: 4 Avg|F|: 0.083 Max|F|: 0.190 Vol.: 2215.7 Time: 0.30m
121 Energy: -268.411148 Log|dE|: -1.105 SCF: 15 Avg|F|: 0.082 Max|F|: 0.194 Vol.: 2215.7 Time: 1.15m
122 Energy: -268.478063 Log|dE|: -1.174 SCF: 15 Avg|F|: 0.081 Max|F|: 0.201 Vol.: 2215.7 Time: 1.14m
123 Energy: -268.452747 Log|dE|: -1.597 SCF: 4 Avg|F|: 0.079 Max|F|: 0.189 Vol.: 2215.7 Time: 0.31m
124 Energy: -268.295591 Log|dE|: -0.804 SCF: 19 Avg|F|: 0.083 Max|F|: 0.188 Vol.: 2215.7 Time: 1.50m
125 Energy: -268.654866 Log|dE|: -0.445 SCF: 21 Avg|F|: 0.083 Max|F|: 0.204 Vol.: 2215.7 Time: 1.65m
126 Energy: -268.380190 Log|dE|: -0.561 SCF: 20 Avg|F|: 0.084 Max|F|: 0.203 Vol.: 2215.7 Time: 1.59m
127 Energy: -268.532470 Log|dE|: -0.817 SCF: 18 Avg|F|: 0.084 Max|F|: 0.207 Vol.: 2215.7 Time: 1.41m
128 Energy: -268.486830 Log|dE|: -1.341 SCF: 15 Avg|F|: 0.083 Max|F|: 0.209 Vol.: 2215.7 Time: 1.13m
129 Energy: -268.514358 Log|dE|: -1.560 SCF: 11 Avg|F|: 0.083 Max|F|: 0.207 Vol.: 2215.7 Time: 0.83m
130 Energy: -268.552395 Log|dE|: -1.420 SCF: 12 Avg|F|: 0.084 Max|F|: 0.214 Vol.: 2215.7 Time: 0.91m
131 Energy: -268.379085 Log|dE|: -0.761 SCF: 20 Avg|F|: 0.084 Max|F|: 0.199 Vol.: 2215.7 Time: 1.56m
132 Energy: -268.362811 Log|dE|: -1.789 SCF: 4 Avg|F|: 0.083 Max|F|: 0.189 Vol.: 2215.7 Time: 0.31m
133 Energy: -268.230803 Log|dE|: -0.879 SCF: 19 Avg|F|: 0.081 Max|F|: 0.184 Vol.: 2215.7 Time: 1.48m
134 Energy: -268.222809 Log|dE|: -2.097 SCF: 4 Avg|F|: 0.081 Max|F|: 0.183 Vol.: 2215.7 Time: 0.31m
135 Energy: -268.225880 Log|dE|: -2.513 SCF: 4 Avg|F|: 0.080 Max|F|: 0.183 Vol.: 2215.7 Time: 0.30m
136 Energy: -268.240746 Log|dE|: -1.828 SCF: 15 Avg|F|: 0.086 Max|F|: 0.203 Vol.: 2215.7 Time: 1.15m
137 Energy: -268.229770 Log|dE|: -1.960 SCF: 15 Avg|F|: 0.083 Max|F|: 0.188 Vol.: 2215.7 Time: 1.17m
138 Energy: -268.239500 Log|dE|: -2.012 SCF: 4 Avg|F|: 0.082 Max|F|: 0.189 Vol.: 2215.7 Time: 0.31m
139 Energy: -268.235624 Log|dE|: -2.412 SCF: 4 Avg|F|: 0.084 Max|F|: 0.189 Vol.: 2215.7 Time: 0.31m
140 Energy: -268.254620 Log|dE|: -1.721 SCF: 12 Avg|F|: 0.079 Max|F|: 0.184 Vol.: 2215.7 Time: 0.91m
141 Energy: -268.282701 Log|dE|: -1.552 SCF: 13 Avg|F|: 0.081 Max|F|: 0.199 Vol.: 2215.7 Time: 1.00m
142 Energy: -268.237084 Log|dE|: -1.341 SCF: 19 Avg|F|: 0.082 Max|F|: 0.185 Vol.: 2215.7 Time: 1.46m
143 Energy: -268.255488 Log|dE|: -1.735 SCF: 4 Avg|F|: 0.082 Max|F|: 0.196 Vol.: 2215.7 Time: 0.31m
144 Energy: -268.205202 Log|dE|: -1.299 SCF: 16 Avg|F|: 0.083 Max|F|: 0.187 Vol.: 2215.7 Time: 1.22m
145 Energy: -268.215894 Log|dE|: -1.971 SCF: 4 Avg|F|: 0.083 Max|F|: 0.189 Vol.: 2215.7 Time: 0.31m
146 Energy: -268.190572 Log|dE|: -1.596 SCF: 5 Avg|F|: 0.083 Max|F|: 0.181 Vol.: 2215.7 Time: 0.38m
147 Energy: -268.127271 Log|dE|: -1.199 SCF: 16 Avg|F|: 0.089 Max|F|: 0.193 Vol.: 2215.7 Time: 1.24m
148 Energy: -268.333709 Log|dE|: -0.685 SCF: 20 Avg|F|: 0.082 Max|F|: 0.196 Vol.: 2215.7 Time: 1.58m
149 Energy: -268.287339 Log|dE|: -1.334 SCF: 18 Avg|F|: 0.083 Max|F|: 0.186 Vol.: 2215.7 Time: 1.37m
150 Energy: -268.305707 Log|dE|: -1.736 SCF: 4 Avg|F|: 0.084 Max|F|: 0.195 Vol.: 2215.7 Time: 0.31m
151 Energy: -268.153521 Log|dE|: -0.818 SCF: 21 Avg|F|: 0.084 Max|F|: 0.183 Vol.: 2215.7 Time: 1.63m
152 Energy: -268.168098 Log|dE|: -1.836 SCF: 4 Avg|F|: 0.084 Max|F|: 0.186 Vol.: 2215.7 Time: 0.31m
153 Energy: -268.167679 Log|dE|: -3.378 SCF: 5 Avg|F|: 0.083 Max|F|: 0.182 Vol.: 2215.7 Time: 0.37m
154 Energy: -268.175326 Log|dE|: -2.117 SCF: 9 Avg|F|: 0.081 Max|F|: 0.173 Vol.: 2215.7 Time: 0.69m
155 Energy: -268.187624 Log|dE|: -1.910 SCF: 9 Avg|F|: 0.084 Max|F|: 0.179 Vol.: 2215.7 Time: 0.70m
156 Energy: -268.180122 Log|dE|: -2.125 SCF: 13 Avg|F|: 0.080 Max|F|: 0.174 Vol.: 2215.7 Time: 0.99m
157 Energy: -268.186525 Log|dE|: -2.194 SCF: 4 Avg|F|: 0.081 Max|F|: 0.176 Vol.: 2215.7 Time: 0.31m
158 Energy: -268.101245 Log|dE|: -1.069 SCF: 20 Avg|F|: 0.085 Max|F|: 0.165 Vol.: 2215.7 Time: 1.54m
159 Energy: -268.158078 Log|dE|: -1.245 SCF: 14 Avg|F|: 0.081 Max|F|: 0.168 Vol.: 2215.7 Time: 1.10m
160 Energy: -268.221476 Log|dE|: -1.198 SCF: 11 Avg|F|: 0.080 Max|F|: 0.176 Vol.: 2215.7 Time: 0.87m
161 Energy: -268.205774 Log|dE|: -1.804 SCF: 10 Avg|F|: 0.080 Max|F|: 0.174 Vol.: 2215.7 Time: 0.76m
162 Energy: -268.198794 Log|dE|: -2.156 SCF: 4 Avg|F|: 0.080 Max|F|: 0.173 Vol.: 2215.7 Time: 0.31m
163 Energy: -268.266214 Log|dE|: -1.171 SCF: 12 Avg|F|: 0.081 Max|F|: 0.177 Vol.: 2215.7 Time: 0.94m
164 Energy: -268.166735 Log|dE|: -1.002 SCF: 18 Avg|F|: 0.082 Max|F|: 0.178 Vol.: 2215.7 Time: 1.41m
165 Energy: -268.285382 Log|dE|: -0.926 SCF: 19 Avg|F|: 0.082 Max|F|: 0.181 Vol.: 2215.7 Time: 1.48m
166 Energy: -268.194406 Log|dE|: -1.041 SCF: 16 Avg|F|: 0.083 Max|F|: 0.180 Vol.: 2215.7 Time: 1.25m
167 Energy: -268.359528 Log|dE|: -0.782 SCF: 20 Avg|F|: 0.082 Max|F|: 0.196 Vol.: 2215.7 Time: 1.57m
168 Energy: -268.295575 Log|dE|: -1.194 SCF: 15 Avg|F|: 0.083 Max|F|: 0.194 Vol.: 2215.7 Time: 1.16m
169 Energy: -268.398718 Log|dE|: -0.987 SCF: 18 Avg|F|: 0.082 Max|F|: 0.203 Vol.: 2215.7 Time: 1.39m
170 Energy: -268.364004 Log|dE|: -1.459 SCF: 10 Avg|F|: 0.082 Max|F|: 0.199 Vol.: 2215.7 Time: 0.77m
171 Energy: -268.363252 Log|dE|: -3.124 SCF: 3 Avg|F|: 0.084 Max|F|: 0.202 Vol.: 2215.7 Time: 0.22m
172 Energy: -268.384988 Log|dE|: -1.663 SCF: 10 Avg|F|: 0.086 Max|F|: 0.221 Vol.: 2215.7 Time: 0.78m
173 Energy: -268.371825 Log|dE|: -1.881 SCF: 12 Avg|F|: 0.082 Max|F|: 0.198 Vol.: 2215.7 Time: 0.92m
174 Energy: -268.370810 Log|dE|: -2.993 SCF: 4 Avg|F|: 0.083 Max|F|: 0.189 Vol.: 2215.7 Time: 0.31m
175 Energy: -268.380027 Log|dE|: -2.035 SCF: 4 Avg|F|: 0.083 Max|F|: 0.206 Vol.: 2215.7 Time: 0.31m
176 Energy: -268.373371 Log|dE|: -2.177 SCF: 6 Avg|F|: 0.084 Max|F|: 0.191 Vol.: 2215.7 Time: 0.45m
177 Energy: -268.382461 Log|dE|: -2.041 SCF: 4 Avg|F|: 0.084 Max|F|: 0.194 Vol.: 2215.7 Time: 0.31m
178 Energy: -268.380689 Log|dE|: -2.752 SCF: 4 Avg|F|: 0.084 Max|F|: 0.194 Vol.: 2215.7 Time: 0.30m
179 Energy: -268.367785 Log|dE|: -1.889 SCF: 5 Avg|F|: 0.082 Max|F|: 0.195 Vol.: 2215.7 Time: 0.39m
180 Energy: -268.367672 Log|dE|: -3.946 SCF: 4 Avg|F|: 0.082 Max|F|: 0.205 Vol.: 2215.7 Time: 0.31m
181 Energy: -268.375155 Log|dE|: -2.126 SCF: 5 Avg|F|: 0.082 Max|F|: 0.190 Vol.: 2215.7 Time: 0.38m
182 Energy: -268.383068 Log|dE|: -2.102 SCF: 4 Avg|F|: 0.083 Max|F|: 0.196 Vol.: 2215.7 Time: 0.31m
183 Energy: -268.220105 Log|dE|: -0.788 SCF: 19 Avg|F|: 0.081 Max|F|: 0.195 Vol.: 2215.7 Time: 1.48m
184 Energy: -268.167162 Log|dE|: -1.276 SCF: 14 Avg|F|: 0.082 Max|F|: 0.181 Vol.: 2215.7 Time: 1.07m
185 Energy: -268.210452 Log|dE|: -1.364 SCF: 15 Avg|F|: 0.080 Max|F|: 0.186 Vol.: 2215.7 Time: 1.13m
186 Energy: -268.281417 Log|dE|: -1.149 SCF: 15 Avg|F|: 0.080 Max|F|: 0.179 Vol.: 2215.7 Time: 1.16m
187 Energy: -268.411548 Log|dE|: -0.886 SCF: 18 Avg|F|: 0.082 Max|F|: 0.190 Vol.: 2215.7 Time: 1.40m
188 Energy: -268.173522 Log|dE|: -0.623 SCF: 20 Avg|F|: 0.082 Max|F|: 0.178 Vol.: 2215.7 Time: 1.60m
189 Energy: -268.319946 Log|dE|: -0.834 SCF: 18 Avg|F|: 0.080 Max|F|: 0.182 Vol.: 2215.7 Time: 1.40m
190 Energy: -268.413019 Log|dE|: -1.031 SCF: 15 Avg|F|: 0.081 Max|F|: 0.186 Vol.: 2215.7 Time: 1.16m
191 Energy: -268.313367 Log|dE|: -1.002 SCF: 16 Avg|F|: 0.083 Max|F|: 0.200 Vol.: 2215.7 Time: 1.25m
192 Energy: -268.873972 Log|dE|: -0.251 SCF: 41 Avg|F|: 0.096 Max|F|: 0.231 Vol.: 2215.7 Time: 3.10m
193 Energy: -268.277126 Log|dE|: -0.224 SCF: 43 Avg|F|: 0.080 Max|F|: 0.185 Vol.: 2215.7 Time: 3.28m
194 Energy: -268.191405 Log|dE|: -1.067 SCF: 16 Avg|F|: 0.081 Max|F|: 0.187 Vol.: 2215.7 Time: 1.24m
195 Energy: -268.447883 Log|dE|: -0.591 SCF: 20 Avg|F|: 0.081 Max|F|: 0.197 Vol.: 2215.7 Time: 1.58m
196 Energy: -268.354178 Log|dE|: -1.028 SCF: 15 Avg|F|: 0.083 Max|F|: 0.202 Vol.: 2215.7 Time: 1.18m

[martin.schlipf]

@1: Restarting from the obtained structure: Assuming you have a calculation with 10 steps where in the 8th step the electronic SCF did not converge, I would restart from the 7th step.

@2: All optimization algorithms (orbitals, density, positions) use the history of inputs and resulting outputs to generate a new input. If you remove the history in every step, you'll end up with linear mixing which will converge much slower in general. However, if some of your history is corrupted by failed electronic SCF this may mean you do not move to the true minimum.

@3: If you notice the default setting does not converge for one of the optimizer, sometimes changing the parameters of this particular optimizer can help. For the ionic relaxation the relevant parameters are IBRION, NFREE, POTIM. You can also not relax all degrees of freedom at the same time to reduce the search space.

[SKM]

Thank you.
will follow the suggestions and if any issue. will consult.
Regards

[SKM]

hi
combining your 1,2,3 suggestions/explanation in previous reply, i tried the convergence of same system [for which i copied the convergence steps summary in previous message]. I traced back where its 'electronic convergence failed but because of default NELM=60, has come out and then moved to next step. So, i considered the ionic positions of the just previous step and then continued the run but this time increasing NELM=200.

Now, the situation is even then the system is not converging rather the energy and the maximum force is fluctuating. Copied the file in the attached zip file. If you see the data the run numbers 282, 295, and 342 have achieved the EDIFF criteria, but the ionic step is not stopped may be because EDIFFG is not fulfilled.

My query is
1. 'will there be systems that never converge but just keep fluctuating at the almost converged energy value?'
2. Why this (my) system is not converging?
INCAR and POSCAR files and the summary of convergence also attached here please.

Regards

[martin.schlipf]

Please carefully read the documentation of the algorithm you use. There are different kind of steps trial and corrector steps that you should be able to distinguish from the OUTCAR file. VASP will only break on trial steps not on corrector steps. EDIFF has no effect on the ionic convergence it is only used for the electronic one. The ionic convergence depends on EDIFFG and IBRION.

If you plot the total energy as a function of steps, you can also clearly see that the energy is still trending downwards. It is not really oscillating. That being said there is also the step 404 which seems to have a much lower energy, so perhaps you can try to restart from that step and see if that energy can be reproduced.

[SKM]

hi
Thank you.
as suggested from the previous run of 404 (copied for ready reference) i did restart run...and results copied in next paragraph

403 Energy: -272.871750 Log|dE|: -2.378 SCF: 4 Avg|F|: 0.075 Max|F|: 0.212 Vol.: 2215.7 Time: 0.31m
404 Energy: -272.956018 Log|dE|: -1.074 SCF: 34 Avg|F|: 0.353 Max|F|: 0.723 Vol.: 2215.7 Time: 2.55m

taken ionic positions at 403 run and restarted calculation. then the iteration summary started as below:
1 Energy: -272.871438 Log|dE|: 2.436 SCF: 53 Avg|F|: 0.026 Max|F|: 0.048 Vol.: 2215.7 Time: 5.66m
2 Energy: -272.871958 Log|dE|: -3.284 SCF: 4 Avg|F|: 0.025 Max|F|: 0.048 Vol.: 2215.7 Time: 0.42m
3 Energy: -272.873969 Log|dE|: -2.696 SCF: 4 Avg|F|: 0.026 Max|F|: 0.049 Vol.: 2215.7 Time: 0.44m
4 Energy: -272.878082 Log|dE|: -2.386 SCF: 4 Avg|F|: 0.027 Max|F|: 0.052 Vol.: 2215.7 Time: 0.44m
5 Energy: -272.886426 Log|dE|: -2.079 SCF: 4 Avg|F|: 0.029 Max|F|: 0.059 Vol.: 2215.7 Time: 0.45m
6 Energy: -272.900120 Log|dE|: -1.864 SCF: 16 Avg|F|: 0.028 Max|F|: 0.074 Vol.: 2215.7 Time: 1.75m
7 Energy: -272.925885 Log|dE|: -1.589 SCF: 13 Avg|F|: 0.041 Max|F|: 0.116 Vol.: 2215.7 Time: 1.46m
8 Energy: -272.965459 Log|dE|: -1.403 SCF: 20 Avg|F|: 0.072 Max|F|: 0.208 Vol.: 2215.7 Time: 2.23m
9 Energy: -272.985165 Log|dE|: -1.705 SCF: 23 Avg|F|: 0.144 Max|F|: 0.415 Vol.: 2215.7 Time: 2.59m
10 Energy: -272.987248 Log|dE|: -2.681 SCF: 18 Avg|F|: 0.120 Max|F|: 0.355 Vol.: 2215.7 Time: 2.00m
11 Energy: -272.989103 Log|dE|: -2.732 SCF: 4 Avg|F|: 0.120 Max|F|: 0.351 Vol.: 2215.7 Time: 0.44m
12 Energy: -272.994801 Log|dE|: -2.244 SCF: 4 Avg|F|: 0.120 Max|F|: 0.347 Vol.: 2215.7 Time: 0.44m
13 Energy: -273.005377 Log|dE|: -1.976 SCF: 10 Avg|F|: 0.118 Max|F|: 0.330 Vol.: 2215.7 Time: 1.12m
14 Energy: -273.025397 Log|dE|: -1.699 SCF: 10 Avg|F|: 0.115 Max|F|: 0.294 Vol.: 2215.7 Time: 1.13m
15 Energy: -273.059671 Log|dE|: -1.465 SCF: 16 Avg|F|: 0.111 Max|F|: 0.243 Vol.: 2215.7 Time: 1.79m
16 Energy: -273.115658 Log|dE|: -1.252 SCF: 16 Avg|F|: 0.109 Max|F|: 0.221 Vol.: 2215.7 Time: 1.81m
17 Energy: -273.157730 Log|dE|: -1.376 SCF: 28 Avg|F|: 0.123 Max|F|: 0.373 Vol.: 2215.7 Time: 3.12m
18 Energy: -273.216038 Log|dE|: -1.234 SCF: 16 Avg|F|: 0.105 Max|F|: 0.303 Vol.: 2215.7 Time: 1.78m
19 Energy: -273.275041 Log|dE|: -1.229 SCF: 13 Avg|F|: 0.088 Max|F|: 0.225 Vol.: 2215.7 Time: 1.49m
20 Energy: -273.330762 Log|dE|: -1.254 SCF: 19 Avg|F|: 0.090 Max|F|: 0.218 Vol.: 2215.7 Time: 2.17m
21 Energy: -273.381564 Log|dE|: -1.294 SCF: 18 Avg|F|: 0.062 Max|F|: 0.147 Vol.: 2215.7 Time: 1.95m
22 Energy: -273.418891 Log|dE|: -1.428 SCF: 15 Avg|F|: 0.056 Max|F|: 0.131 Vol.: 2215.7 Time: 1.67m
23 Energy: -273.387727 Log|dE|: -1.506 SCF: 16 Avg|F|: 0.117 Max|F|: 0.440 Vol.: 2215.7 Time: 1.81m
24 Energy: -273.424494 Log|dE|: -1.435 SCF: 20 Avg|F|: 0.066 Max|F|: 0.194 Vol.: 2215.7 Time: 2.23m
25 Energy: -273.462459 Log|dE|: -1.421 SCF: 15 Avg|F|: 0.041 Max|F|: 0.100 Vol.: 2215.7 Time: 1.65m
26 Energy: -273.475207 Log|dE|: -1.895 SCF: 11 Avg|F|: 0.043 Max|F|: 0.120 Vol.: 2215.7 Time: 1.23m
27 Energy: -273.458468 Log|dE|: -1.776 SCF: 18 Avg|F|: 0.086 Max|F|: 0.344 Vol.: 2215.7 Time: 1.98m
28 Energy: -273.476807 Log|dE|: -1.737 SCF: 17 Avg|F|: 0.051 Max|F|: 0.151 Vol.: 2215.7 Time: 1.88m
29 Energy: -273.504298 Log|dE|: -1.561 SCF: 17 Avg|F|: 0.037 Max|F|: 0.113 Vol.: 2215.7 Time: 1.84m
30 Energy: -273.517401 Log|dE|: -1.883 SCF: 17 Avg|F|: 0.050 Max|F|: 0.178 Vol.: 2215.7 Time: 1.88m
31 Energy: -273.542511 Log|dE|: -1.600 SCF: 12 Avg|F|: 0.037 Max|F|: 0.070 Vol.: 2215.7 Time: 1.35m
32 Energy: -273.549175 Log|dE|: -2.176 SCF: 10 Avg|F|: 0.040 Max|F|: 0.078 Vol.: 2215.7 Time: 1.10m
33 Energy: -273.548429 Log|dE|: -3.127 SCF: 18 Avg|F|: 0.060 Max|F|: 0.197 Vol.: 2215.7 Time: 1.95m
34 Energy: -273.551699 Log|dE|: -2.485 SCF: 10 Avg|F|: 0.049 Max|F|: 0.122 Vol.: 2215.7 Time: 1.10m
35 Energy: -273.574933 Log|dE|: -1.634 SCF: 15 Avg|F|: 0.039 Max|F|: 0.083 Vol.: 2215.7 Time: 1.66m
36 Energy: -273.582279 Log|dE|: -2.134 SCF: 13 Avg|F|: 0.044 Max|F|: 0.112 Vol.: 2215.7 Time: 1.44m
37 Energy: -273.607767 Log|dE|: -1.594 SCF: 17 Avg|F|: 0.030 Max|F|: 0.074 Vol.: 2215.7 Time: 1.85m
38 Energy: -273.619163 Log|dE|: -1.943 SCF: 17 Avg|F|: 0.043 Max|F|: 0.101 Vol.: 2215.7 Time: 1.86m
39 Energy: -273.642119 Log|dE|: -1.639 SCF: 12 Avg|F|: 0.034 Max|F|: 0.075 Vol.: 2215.7 Time: 1.34m
40 Energy: -273.650442 Log|dE|: -2.080 SCF: 12 Avg|F|: 0.036 Max|F|: 0.108 Vol.: 2215.7 Time: 1.32m
41 Energy: -273.655442 Log|dE|: -2.301 SCF: 19 Avg|F|: 0.054 Max|F|: 0.211 Vol.: 2215.7 Time: 2.07m
42 Energy: -273.668396 Log|dE|: -1.888 SCF: 12 Avg|F|: 0.050 Max|F|: 0.194 Vol.: 2215.7 Time: 1.31m
43 Energy: -273.695813 Log|dE|: -1.562 SCF: 18 Avg|F|: 0.048 Max|F|: 0.139 Vol.: 2215.7 Time: 2.00m
44 Energy: -273.708387 Log|dE|: -1.901 SCF: 20 Avg|F|: 0.078 Max|F|: 0.175 Vol.: 2215.7 Time: 2.24m
45 Energy: -273.710351 Log|dE|: -2.707 SCF: 13 Avg|F|: 0.067 Max|F|: 0.114 Vol.: 2215.7 Time: 1.44m
46 Energy: -273.742349 Log|dE|: -1.495 SCF: 16 Avg|F|: 0.047 Max|F|: 0.087 Vol.: 2215.7 Time: 1.78m
47 Energy: -273.762696 Log|dE|: -1.691 SCF: 19 Avg|F|: 0.049 Max|F|: 0.128 Vol.: 2215.7 Time: 2.10m
48 Energy: -273.755658 Log|dE|: -2.153 SCF: 21 Avg|F|: 0.094 Max|F|: 0.252 Vol.: 2215.7 Time: 2.35m
49 Energy: -273.767551 Log|dE|: -1.925 SCF: 18 Avg|F|: 0.065 Max|F|: 0.175 Vol.: 2215.7 Time: 2.00m
50 Energy: -273.802768 Log|dE|: -1.453 SCF: 18 Avg|F|: 0.058 Max|F|: 0.158 Vol.: 2215.7 Time: 2.00m
51 Energy: -273.862105 Log|dE|: -1.227 SCF: 27 Avg|F|: 0.079 Max|F|: 0.204 Vol.: 2215.7 Time: 2.98m
52 Energy: -273.944994 Log|dE|: -1.082 SCF: 22 Avg|F|: 0.066 Max|F|: 0.157 Vol.: 2215.7 Time: 2.46m
53 Energy: -274.143488 Log|dE|: -0.702 SCF: 29 Avg|F|: 0.119 Max|F|: 0.263 Vol.: 2215.7 Time: 3.25m
54 Energy: -274.251117 Log|dE|: -0.968 SCF: 34 Avg|F|: 0.310 Max|F|: 0.780 Vol.: 2215.7 Time: 3.83m
55 Energy: -274.262614 Log|dE|: -1.939 SCF: 23 Avg|F|: 0.234 Max|F|: 0.543 Vol.: 2215.7 Time: 2.62m
56 Energy: -274.267095 Log|dE|: -2.349 SCF: 21 Avg|F|: 0.263 Max|F|: 0.634 Vol.: 2215.7 Time: 2.33m
57 Energy: -274.281753 Log|dE|: -1.834 SCF: 13 Avg|F|: 0.266 Max|F|: 0.639 Vol.: 2215.7 Time: 1.40m
58 Energy: -274.307558 Log|dE|: -1.588 SCF: 17 Avg|F|: 0.273 Max|F|: 0.648 Vol.: 2215.7 Time: 1.84m
59 Energy: -274.354092 Log|dE|: -1.332 SCF: 21 Avg|F|: 0.282 Max|F|: 0.673 Vol.: 2215.7 Time: 2.31m
60 Energy: -274.417095 Log|dE|: -1.201 SCF: 24 Avg|F|: 0.303 Max|F|: 0.718 Vol.: 2215.7 Time: 2.67m
61 Energy: -274.421567 Log|dE|: -2.350 SCF: 29 Avg|F|: 0.344 Max|F|: 0.804 Vol.: 2215.7 Time: 3.29m
62 Energy: -274.445348 Log|dE|: -1.624 SCF: 25 Avg|F|: 0.323 Max|F|: 0.764 Vol.: 2215.7 Time: 2.80m
63 Energy: -274.541590 Log|dE|: -1.017 SCF: 12 Avg|F|: 0.306 Max|F|: 0.689 Vol.: 2215.7 Time: 1.34m
64 Energy: -274.789254 Log|dE|: -0.606 SCF: 13 Avg|F|: 0.258 Max|F|: 0.480 Vol.: 2215.7 Time: 1.50m
65 Energy: -275.093210 Log|dE|: -0.517 SCF: 22 Avg|F|: 0.204 Max|F|: 0.404 Vol.: 2215.7 Time: 2.48m
66 Energy: -274.926348 Log|dE|: -0.778 SCF: 27 Avg|F|: 0.319 Max|F|: 1.281 Vol.: 2215.7 Time: 3.05m
67 Energy: -275.155462 Log|dE|: -0.640 SCF: 29 Avg|F|: 0.214 Max|F|: 0.629 Vol.: 2215.7 Time: 3.23m
68 Energy: -275.307569 Log|dE|: -0.818 SCF: 15 Avg|F|: 0.184 Max|F|: 0.393 Vol.: 2215.7 Time: 1.68m
69 Energy: -275.593122 Log|dE|: -0.544 SCF: 20 Avg|F|: 0.149 Max|F|: 0.324 Vol.: 2215.7 Time: 2.26m
70 Energy: -275.545743 Log|dE|: -1.324 SCF: 17 Avg|F|: 0.261 Max|F|: 1.278 Vol.: 2215.7 Time: 1.94m
71 Energy: -275.672422 Log|dE|: -0.897 SCF: 25 Avg|F|: 0.184 Max|F|: 0.733 Vol.: 2215.7 Time: 2.79m
72 Energy: -275.880305 Log|dE|: -0.682 SCF: 16 Avg|F|: 0.135 Max|F|: 0.340 Vol.: 2215.7 Time: 1.80m
73 Energy: -275.984893 Log|dE|: -0.981 SCF: 16 Avg|F|: 0.116 Max|F|: 0.294 Vol.: 2215.7 Time: 1.80m
74 Energy: -275.995112 Log|dE|: -1.991 SCF: 12 Avg|F|: 0.124 Max|F|: 0.287 Vol.: 2215.7 Time: 1.34m
75 Energy: -276.106909 Log|dE|: -0.952 SCF: 12 Avg|F|: 0.082 Max|F|: 0.188 Vol.: 2215.7 Time: 1.37m
76 Energy: -276.166532 Log|dE|: -1.225 SCF: 18 Avg|F|: 0.070 Max|F|: 0.139 Vol.: 2215.7 Time: 1.98m
77 Energy: -276.172198 Log|dE|: -2.247 SCF: 11 Avg|F|: 0.077 Max|F|: 0.144 Vol.: 2215.7 Time: 1.22m
78 Energy: -276.228946 Log|dE|: -1.246 SCF: 14 Avg|F|: 0.056 Max|F|: 0.112 Vol.: 2215.7 Time: 1.57m
79 Energy: -276.263254 Log|dE|: -1.465 SCF: 19 Avg|F|: 0.065 Max|F|: 0.178 Vol.: 2215.7 Time: 2.10m
80 Energy: -276.311414 Log|dE|: -1.317 SCF: 15 Avg|F|: 0.051 Max|F|: 0.079 Vol.: 2215.7 Time: 1.67m
81 Energy: -276.326195 Log|dE|: -1.830 SCF: 15 Avg|F|: 0.058 Max|F|: 0.118 Vol.: 2215.7 Time: 1.64m
82 Energy: -276.318456 Log|dE|: -2.111 SCF: 20 Avg|F|: 0.095 Max|F|: 0.222 Vol.: 2215.7 Time: 2.19m
83 Energy: -276.329108 Log|dE|: -1.973 SCF: 18 Avg|F|: 0.067 Max|F|: 0.139 Vol.: 2215.7 Time: 1.96m
84 Energy: -276.377295 Log|dE|: -1.317 SCF: 18 Avg|F|: 0.058 Max|F|: 0.122 Vol.: 2215.7 Time: 1.97m
85 Energy: -276.438898 Log|dE|: -1.210 SCF: 21 Avg|F|: 0.075 Max|F|: 0.181 Vol.: 2215.7 Time: 2.33m
86 Energy: -276.377150 Log|dE|: -1.209 SCF: 26 Avg|F|: 0.184 Max|F|: 0.452 Vol.: 2215.7 Time: 2.92m
87 Energy: -276.448154 Log|dE|: -1.149 SCF: 27 Avg|F|: 0.095 Max|F|: 0.242 Vol.: 2215.7 Time: 2.99m
88 Energy: -276.485590 Log|dE|: -1.427 SCF: 13 Avg|F|: 0.091 Max|F|: 0.213 Vol.: 2215.7 Time: 1.44m
89 Energy: -276.583576 Log|dE|: -1.009 SCF: 19 Avg|F|: 0.094 Max|F|: 0.266 Vol.: 2215.7 Time: 2.14m
90 Energy: -276.661648 Log|dE|: -1.108 SCF: 30 Avg|F|: 0.163 Max|F|: 0.413 Vol.: 2215.7 Time: 3.39m
91 Energy: -276.682677 Log|dE|: -1.677 SCF: 18 Avg|F|: 0.164 Max|F|: 0.400 Vol.: 2215.7 Time: 2.04m
92 Energy: -276.710726 Log|dE|: -1.552 SCF: 19 Avg|F|: 0.170 Max|F|: 0.408 Vol.: 2215.7 Time: 2.08m
93 Energy: -276.712352 Log|dE|: -2.789 SCF: 16 Avg|F|: 0.192 Max|F|: 0.558 Vol.: 2215.7 Time: 1.83m
94 Energy: -276.721562 Log|dE|: -2.036 SCF: 16 Avg|F|: 0.178 Max|F|: 0.466 Vol.: 2215.7 Time: 1.80m
95 Energy: -276.796978 Log|dE|: -1.123 SCF: 5 Avg|F|: 0.167 Max|F|: 0.409 Vol.: 2215.7 Time: 0.56m
96 Energy: -276.966637 Log|dE|: -0.770 SCF: 23 Avg|F|: 0.124 Max|F|: 0.229 Vol.: 2215.7 Time: 2.54m
97 Energy: -277.065773 Log|dE|: -1.004 SCF: 20 Avg|F|: 0.163 Max|F|: 0.643 Vol.: 2215.7 Time: 2.27m
98 Energy: -277.168805 Log|dE|: -0.987 SCF: 13 Avg|F|: 0.150 Max|F|: 0.501 Vol.: 2215.7 Time: 1.47m
99 Energy: -277.286901 Log|dE|: -0.928 SCF: 20 Avg|F|: 0.142 Max|F|: 0.389 Vol.: 2215.7 Time: 2.20m
100 Energy: -277.305447 Log|dE|: -1.732 SCF: 29 Avg|F|: 0.195 Max|F|: 0.716 Vol.: 2215.7 Time: 3.20m

--------- -----
still the run not converged...
(1)cant we observe the Max Force in the system or average force which seems not continuously reducing?
(2)i got very few such situations before....but i some times took if the energy fluctuation over last steps less than 20meV depends on not so much importance of energy value for that particular instance, i used to stop the run. is this logical and reasonable?

Regards

[martin.schlipf]

Well, the structure is still converging. As long as you still see such significant changes to the total energy, it is worth continuing the relaxation. The most likely case is that you chose a bad starting position. Compared to one of your first posts, the structure seems to be significantly lower in energy, so VASP is doing what is expected.

37 Energy: -268.166505 Log|dE|: -1.353 SCF: 13 Avg|F|: 0.081 Max|F|: 0.202 Vol.: 2215.7 Time: 1.00m

100 Energy: -277.305447 Log|dE|: -1.732 SCF: 29 Avg|F|: 0.195 Max|F|: 0.716 Vol.: 2215.7 Time: 3.20m

But there is really not much you can do other then what was already suggested. Perhaps IBRION=3 would have been better, but it this is hard to judge a priori. One thing you should do is double check the structure by looking at it across the trajectory. Perhaps you spot an error in the setup.

For IBRION=0, a molecular dynamics is performed, whereas all other algorithms are destined for relaxations into a local energy minimum. For difficult relaxation problems it is recommended to use the conjugate gradient algorithm (IBRION=2), which presently possesses the most reliable backup routines. Damped molecular dynamics (IBRION=3) are often useful when starting from very bad initial guesses. Close to the local minimum the RMM-DIIS (IBRION=1) is usually the best choice. IBRION=5 and IBRION=6 are using finite differences to determine the second derivatives (Hessian matrix and phonon frequencies), whereas IBRION=7 and IBRION=8 use density functional perturbation theory to calculate the derivatives. (link)

[SKM]

The most likely case is that you chose a bad starting position.

i think you are right in this specific case. In fact the primitive .cif file shows its a fractional atomic occupancy. But when i converted to VASP format, the POSCAR file did not show up one atom completely. But i manually replaced one of the atoms with that of missing atoms. See below the original .cif file and the converted VASP format (i.e. POSCAR file) and the manually edited POSCAR (or VASP format) file.attached.

As partial occupancy was the key factor here and my manual intervention is the culprit for convergence issues?

also attaching in additional reply with the current CONTCAR structure, with an initial vacuum added to create slab model. (as max 3 attachments allowed)

Regards

[SKM]

the additional files attached, please.
Ready reference the INCAR is

# PREC = Normal
NPAR=12
IBRION = 2
POTIM = 0.1
#ISIF = 2
# ENCUT = 450
EDIFF = 1.0e-05
EDIFFG = 1e-04
IVDW = 11
ISMEAR = 0; SIGMA = 0.01
IALGO = 48
LREAL = Auto
LWAVE = .FALSE.
LCHARG = .FALSE.
ADDGRID = .TRUE.
#ISYM = 2
#SYMPREC = 1e-05
AMIX = 0.01
NELM = 200
NSW=500
NBANDS = 828

[martin.schlipf]

Yes this will not work like this. The fractional occupations should not all be filled, like what the conversion did. Instead you need to create a supercell and then randomly fill the sites according to the occupancy. Probably you would need to round it to 1/3 occupancy for Bi and Ag and 1/6 for Cu otherwise you don't get reasonable cell sizes.
Still, for a long time I would have recommended against these kind of calculations with DFT, because it is very hard to get the statistics right. But now with machine learning it may be actually possible to do these kind of calculations. You should discuss a strategy to tackle this issue with your PI. But please start with the bulk material before you do any surfaces.