# [CP2K-user] Trying to understand the output from neb(band) module

fa...@gmail.com fabia... at gmail.com
Sat Nov 14 07:52:45 UTC 2020

```Dear Wei,

The force acting on an atom is a vector. The net force is equal to the
length of this vector which is computed as the norm, not a simple sum.

Best,
Fabian

On Saturday, 14 November 2020 at 00:15:01 UTC+1 we... at gmail.com wrote:

> Hi Fabian,
>
> Thanks for the clarification.  What you pointed out makes sense.  However,
> I wonder if that was the best way to control convergence.  Let's say your
> x, y, z forces are 0.1 -0.1 0.001.  The net force will be 0.001.  If the
> max force is set to be 0.002 in the convergence control, this looks fine
> but we probably shouldn't say the force is converged.
>
> Wei
>
>
> On Friday, November 13, 2020 at 2:25:51 AM UTC-5 fa... at gmail.com wrote:
>
>> Hi,
>>
>> The the force on the first atom of replica Nr. 6 has the components
>> 0.024362977  -0.000274819  -0.000383546, which results in a net force of
>> 0.0244. This is precisely what is reported by cp2k.
>>
>> Best,
>> Fabian
>>
>> On Friday, 13 November 2020 at 04:27:44 UTC+1 we... at gmail.com wrote:
>>
>>> I was playing with the neb tutorial at
>>> https://www.cp2k.org/exercises:2016_uzh_cmest:path_optimization_neb
>>> and was using all input files from this site.
>>>
>>>
>>>
>>> After the second band step, the separate band output gave the following
>>> convergence check:
>>>
>>>
>>> *******************************************************************************
>>>
>>>  RMS DISPLACEMENT =   0.01661     [
>>> 0.00010]                               ( NO)
>>>
>>>  MAX DISPLACEMENT =   0.04582     [
>>> 0.00020]                               ( NO)
>>>
>>>  RMS FORCE        =   0.00459     [
>>> 0.00500]                               (YES)
>>>
>>>  MAX FORCE        =   0.02442     [
>>> 0.00100]                               ( NO)
>>>
>>>
>>>  *******************************************************************************
>>>
>>>
>>>
>>> *The screen output has the following energies and force values.  What is
>>> odd that the max force of all these images is not 0.02442.  Actually there
>>> is no force that is close to be +-0.0244.  I am wondering what is this “MAX
>>> FORCE”. Thanks.*
>>>
>>>
>>>
>>>  NEB| Computing Energies and Forces
>>>
>>>  NEB| REPLICA Nr.    1- Energy and Forces
>>>
>>>  NEB|                                     Total Energy:
>>> -14.955972284
>>>
>>>  NEB|    ATOM                            X
>>> Y                Z
>>>
>>>  NEB|      C                      -0.000158132     -0.000000000
>>> -0.000010247
>>>
>>>  NEB|      C                       0.000158132      0.000000000
>>> 0.000010247
>>>
>>>  NEB|      H                      -0.000009893     -0.000000000
>>> 0.000090633
>>>
>>>  NEB|      H                      -0.000044050     -0.000068824
>>> -0.000011886
>>>
>>>  NEB|      H                      -0.000044050      0.000068824
>>> -0.000011886
>>>
>>>  NEB|      H                       0.000009893      0.000000000
>>> -0.000090633
>>>
>>>  NEB|      H                       0.000044050      0.000068824
>>> 0.000011886
>>>
>>>  NEB|      H                       0.000044050     -0.000068824
>>> 0.000011886
>>>
>>>  NEB| REPLICA Nr.    2- Energy and Forces
>>>
>>>  NEB|                                     Total Energy:
>>> -14.953424807
>>>
>>>  NEB|    ATOM                            X
>>> Y                Z
>>>
>>>  NEB|      C                       0.015511582     -0.000123867
>>> -0.000363499
>>>
>>>  NEB|      C                      -0.015514484      0.000198863
>>> 0.000377792
>>>
>>>  NEB|      H                       0.000857207      0.000192596
>>> 0.003925016
>>>
>>>  NEB|      H                       0.000684401     -0.003902176
>>> -0.002099542
>>>
>>>  NEB|      H                       0.000794070      0.003497209
>>> -0.002176137
>>>
>>>  NEB|      H                      -0.000859132      0.000183216
>>> -0.003909916
>>>
>>>  NEB|      H                      -0.000734015      0.003669315
>>> 0.002258834
>>>
>>>  NEB|      H                      -0.000739709     -0.003761630
>>> 0.001987922
>>>
>>>  NEB| REPLICA Nr.    3- Energy and Forces
>>>
>>>  NEB|                                     Total Energy:
>>> -14.952203598
>>>
>>>  NEB|    ATOM                            X
>>> Y                Z
>>>
>>>  NEB|      C                       0.010538684     -0.000238117
>>> -0.000516915
>>>
>>>  NEB|      C                      -0.010542876      0.000214692
>>> 0.000522403
>>>
>>>  NEB|      H                       0.000413313     -0.000291891
>>> 0.003136219
>>>
>>>  NEB|      H                       0.000191793     -0.002982635
>>> -0.002211249
>>>
>>>  NEB|      H                       0.000330883      0.003013668
>>> -0.001368350
>>>
>>>  NEB|      H                      -0.000425288     -0.000291342
>>> -0.003075548
>>>
>>>  NEB|      H                      -0.000246337      0.003274227
>>> 0.001455731
>>>
>>>  NEB|      H                      -0.000260278     -0.002823871
>>> 0.002056329
>>>
>>>  NEB| REPLICA Nr.    4- Energy and Forces
>>>
>>>  NEB|                                     Total Energy:
>>> -14.951836807
>>>
>>>  NEB|    ATOM                            X
>>> Y                Z
>>>
>>>  NEB|      C                      -0.000166119     -0.000233856
>>> -0.000487654
>>>
>>>  NEB|      C                       0.000160984      0.000258427
>>> 0.000483064
>>>
>>>  NEB|      H                       0.000029046      0.000183156
>>> 0.000057179
>>>
>>>  NEB|      H                      -0.000172411     -0.000483736
>>> -0.000359493
>>>
>>>  NEB|      H                      -0.000023827      0.000096042
>>>     -0.000156766
>>>
>>>  NEB|      H                      -0.000040779      0.000199584
>>> 0.000032287
>>>
>>>  NEB|      H                       0.000106393      0.000381211
>>> 0.000225999
>>>
>>>  NEB|      H                       0.000106826     -0.000345313
>>> 0.000203051
>>>
>>>  NEB| REPLICA Nr.    5- Energy and Forces
>>>
>>>  NEB|                                     Total Energy:
>>> -14.951407301
>>>
>>>  NEB|    ATOM                            X
>>> Y                Z
>>>
>>>  NEB|      C                       0.015874406     -0.000326490
>>> -0.000555730
>>>
>>>  NEB|      C                      -0.015842202      0.000299497
>>> 0.000559685
>>>
>>>  NEB|      H                       0.000535731     -0.002915118
>>> 0.002845326
>>>
>>>  NEB|      H                       0.000312063     -0.001213868
>>> -0.004546885
>>>
>>>  NEB|      H                       0.000505489      0.003928930
>>> 0.001110436
>>>
>>>  NEB|      H                      -0.000585448     -0.002832671
>>> -0.002713428
>>>
>>>  NEB|      H                      -0.000406024      0.004307148
>>> -0.001105774
>>>
>>>  NEB|      H                      -0.000394296     -0.001114621
>>> 0.004405311
>>>
>>>  NEB| REPLICA Nr.    6- Energy and Forces
>>>
>>>  NEB|                                     Total Energy:
>>> -14.952232632
>>>
>>>  NEB|    ATOM                            X
>>> Y                Z
>>>
>>>  NEB|      C                       0.024362977     -0.000274819
>>> -0.000383546
>>>
>>>  NEB|      C                      -0.024281416      0.000284322
>>> 0.000400750
>>>
>>>  NEB|      H                       0.001292285     -0.004167767
>>> 0.002626455
>>>
>>>  NEB|      H                       0.001137983     -0.000313475
>>> -0.005288164
>>>
>>>  NEB|      H                       0.001311947      0.004206108
>>> 0.002313869
>>>
>>>  NEB|      H                      -0.001362979     -0.004056262
>>> -0.002510384
>>>
>>>  NEB|      H                      -0.001240025      0.004537593
>>> -0.002369052
>>>
>>>  NEB|      H                      -0.001219620     -0.000261211
>>> 0.005209053
>>>
>>>  NEB| REPLICA Nr.    7- Energy and Forces
>>>
>>>  NEB|                                     Total Energy:
>>> -14.954539124
>>>
>>>  NEB|    ATOM                            X
>>> Y                Z
>>>
>>>  NEB|      C                       0.016039728     -0.000166622
>>> -0.000179795
>>>
>>>  NEB|      C                      -0.015936746      0.000181883
>>> 0.000203661
>>>
>>>  NEB|      H                       0.000838326     -0.004015114
>>> 0.002084504
>>>
>>>  NEB|      H                       0.000753054      0.000204003
>>> -0.004717897
>>>
>>>  NEB|      H                       0.000870997      0.003741728
>>> 0.002384503
>>>
>>>  NEB|      H                      -0.000902028     -0.003947288
>>> -0.002036799
>>>
>>>  NEB|      H                      -0.000843340      0.003959916
>>> -0.002460137
>>>
>>>  NEB|      H                      -0.000819474      0.000224363
>>> 0.004721034
>>>
>>>  NEB| REPLICA Nr.    8- Energy and Forces
>>>
>>>  NEB|                                     Total Energy:
>>> -14.955953570
>>>
>>>  NEB|    ATOM                            X
>>> Y                Z
>>>
>>>  NEB|      C                      -0.000000797      0.000124456
>>> 0.000066034
>>>
>>>  NEB|      C                       0.000011951     -0.000146750
>>> -0.000118626
>>>
>>>  NEB|      H                       0.000029286      0.000146761
>>> 0.000101230
>>>
>>>  NEB|      H                      -0.000005088     -0.000168487
>>> -0.000042189
>>>
>>>  NEB|      H                       0.000005136      0.000121871
>>> -0.000047943
>>>
>>>  NEB|      H                      -0.000007405     -0.000110873
>>> -0.000237047
>>>
>>>  NEB|      H                      -0.000035252      0.000164078
>>>  0.000019902
>>>
>>>  NEB|      H                      -0.000000769     -0.000171696
>>> 0.000257590
>>>
>>
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