# Too slow for 1008 Ni atoms, 20 or more minutes per step

yell... at gmail.com yell... at gmail.com
Wed Apr 12 09:17:19 UTC 2017

```

Task was waiting in the queue yesterday. The simulation time per step is
reduced obviously.

But the speed gets slower because of the increasing of SCF cycles.

# Step Nr. Time[fs] Kin.[a.u.] Temp[K] Pot.[a.u.] Cons Qty[a.u.] UsedTime[s]

0 0.000000 9.566949152 2000.000000000 -170530.032653392 -170520.455919565
0.000000000

1 1.000000 9.631592301 2013.513848184 -170530.197758967 -170520.559182878
3368.403749943

2 2.000000 9.844516264 2058.026254206 -170530.614774376 -170520.760553775
119.362696171

3 3.000000 10.134210226 2118.587663569 -170531.251818051 -170521.099615591
140.031235933

103 103.000000 5.131475709 1072.750701983 -170544.302114205
-170530.046201117 479.899127960

104 104.000000 5.085703611 1063.181904658 -170544.285813199
-170530.018294504 466.044290066

105 105.000000 5.031751308 1051.903010733 -170544.056415561
-170529.785912487 447.755058050

122 122.000000 6.246773076 1305.907029920 -170546.291929917
-170529.923306198 866.148313046

123 123.000000 6.724651351 1405.808945809 -170545.774218367
-170528.879454790 852.673817873

124 124.000000 7.087707135 1481.706868681 -170545.226813770
-170527.918999875 866.536659002

Is the following phenomenon normal?

*** SCF run converged in     1 steps ***

Leaving inner SCF loop after reaching    20 steps.

Best regards,

Huang

>
> *1. the system(containing more than 1000 atoms) is too big;*
> *2. using PREFERRED_DIAG_LIBRARY
> <https://manual.cp2k.org/trunk/CP2K_INPUT/GLOBAL.html#list_PREFERRED_DIAG_LIBRARY> in CP2K_INPUT
> <https://manual.cp2k.org/trunk/CP2K_INPUT.html> / GLOBAL
> <https://manual.cp2k.org/trunk/CP2K_INPUT/GLOBAL.html> section can speedup
> the simulation, set PREFERRED_DIAG_LIBRARY=ELPA, but you should install
> elpa     library before using it;*
> *3. the cutoff may be too small, the bigger values will be slower;*
> *4. the EPS_SCF is too big,  tunning it to small( for example, 4.0E-7, the
> simulation will be slower);*
> *5. using the relaxed system can speedup convergence.*
>
>
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