[CP2K:6967] Re: Re-optimising transition state using dimer method

luca lcb... at gmail.com
Tue Sep 8 13:27:28 UTC 2015

Dear Tobias,
you are refining a TS state obtained from NEB,  thus, you have a "good"
starting point.
Nevertheless, the dimer-algorithm assigns the directions of the dimer in
random way, thus, in this case,  the random assignement affects
negatively the convergence of the refininement, preventing the

Provide the right dimer-directions in agreement with the imaginary mode 
is the right choice, however, I would suggest to use a proper set-up of
the input parameters to avoid extra work.

-1- See J. Org. Chem., 2013, 78 (5), pp 2118–2127
DOI: 10.1021/jo3023439
I this work I used this set-up:

        DR [angstrom] 0.01
          OPTIMIZER CG
          MAX_ITER  12           #INCREASE!
            MAX_STEEP_STEPS 0
              TYPE 2PNT

Anyway, the parameters are system dependent, so you have to try
different set-up.

-2- In your case, to obtain the right directions of the dimers, you can
increase the MAX_ITER keyword, at least for the first few search steps.
Because you are near the TS, increasing the MAX_ITER, the algorithm
should find the dimer directions for the local imaginary mode, which
should be the imaginary mode obtained by the vibrational analysis.


> thanks for the quick reply. I was thinking along similar lines, since
> I was wondering how the optimiser would know which direction to follow
> (for other quantum chemical codes you would have to provide force
> constants in one way or other). Now, having not used this keyword in
> CP2K before, could you be a bit more specific about the format?
> According to the manual, one would explicitly specify the dimer vector
> in this input section, i.e. ideally I would use the imaginary mode for
> this.I simply copy this from the _frequenxies.mol output file (the one
> I have specified to read with molden). Hence the section would look
> like this:
>   &GEO_OPT
>         &DIMER
>         &ROT_OPT
>           OPTIMIZER CG
>         &END ROT_OPT
>         &DIMER_VECTOR
>             -0.000030      -0.000001      -0.000005
>              0.000019       0.000008       0.000023
>             -0.000008      -0.000017      -0.000007
>          <remaining lines>
>        &END DIMER
>     MAX_FORCE 8.0E-4
>     MAX_ITER 500
>   &PRINT
>       &EACH
>          GEO_OPT 1
>       &END EACH
>   &END
> Tobias
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