Re-optimising transition state using dimer method

Tobias Kraemer 161brun... at
Tue Sep 8 10:11:48 UTC 2015

Dear SL,

thanks for clarification. The calculation did work now, however, the 
outcome was somewhat unexpected. The structure converged to a minimum, 
although I asked
for a transition state optimisation. To be clear, the input geometry is 
very close to a good transition state (it comes from a CI-NEB calculation). 
The vibrational analysis revealed a prominent imaginary mode which 
corresponds to the desired reaction channel. A second, much smaller (10s 
cm-1) imagrinary mode was found, which involved a small rotation of a group 
in the side chain. I want to get rid of this mode, and to this end, I 
displaced the structure along the smaller imaginary mode (using the scaled 
displacement vector from the vibrational analysis). I was hoping that with 
such a good guess of the TS structure, it should be straightforward to 
converge to the desired TS (with only one large imaginary mode). The fact 
that the structure fell back into a minimum suggests to me, that I have 
done something wrong. I have uploaded the input along with the starting 
structure and the trajectory of the optimisation [note the structure is 
quite large, the reaction happens at centre Rh(277)]. 

I am particularly keen to learn which parameters I may have to change, or 
if I am even providing the right input structure. From the test examples in 
CP2K distribution it appears to me that providing one structure is 
suffcient (these test cases ran without a problem, however, they are very 
small systems).

At this stage it would be crucial for me to work out the protocols for 
running these type of calculations, since there are are number of TSs along 
a complex pathway which I need to locate. I presume that the present case 
won't be the only tricky TS which will need re-optimisation. As a note 
aside, a constrained optimisation on the same system yielded the desired 
TS, but this is only possible in cases, where the change in geometry does 
not affect the core structure of the reaction coordinate to large extend. I 
have dealt with situations in the meantime, where this method does not 
work, and I would be relying on the dimer method.

Thanks for your comments, much appreciated



On Tuesday, September 1, 2015 at 5:11:13 PM UTC+1, Tobias Kraemer wrote:
> Hi all,
> I am trying to re-optimise a transition state structure which has a 
> spurious (small) imaginary mode on top of the large imaginary mode which 
> corresponds to the transition state. I've also tested doing a constrained 
> optimisation fixing selected atoms involved in the transition state, which 
> also worked in this particular case. Howeve, I would also like to try our 
> the dimer method for the purpose of re-optimising a transition state 
> structure. To this end, I have composed an input, however, the job crashes 
> and I keep getting an error message about certain line Search type not 
> being implemented (looks quite obvious from the message). However, I can't 
> seem to find what I need to change to make it work. Your advice would be 
> much appreciated. The motion section can be found below, full input file 
> also uploaded. 
> Any ideas on how to correctly set up a calculation using the dimer method 
> are welcome
> Thanks for your help
> Tobias
>  ************************************************************************
>  *** 16:48:48 ERRORL2 in cg_utils:cg_linmin processor 0  :: err=-1000 ***
>  *** UNIMPLEMENTED, Line Search type not yet implemented in CG for TS ***
>  *** search.                                                          ***
>  ************************************************************************
>  ===== Routine Calling Stack =====
>            10 cg_linmin
>             9 cp_cg_main
>             8 geoopt_cg
>             7 cp_rot_opt
>             6 cp_eval_at_ts
>             5 cp_eval_at
>             4 cp_cg_main
>             3 geoopt_cg
>             2 cp_geo_opt
>             1 CP2K
>   &GEO_OPT
>         &DIMER
>         &ROT_OPT
>           OPTIMIZER CG
>         &END ROT_OPT
>        &END DIMER
>     MAX_FORCE 8.0E-4
>     MAX_ITER 500
>   &PRINT
>       &EACH
>          GEO_OPT 1
>       &END EACH
>   &END
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