[CP2K:6980] Re: Re-optimising transition state using dimer method

[luca]

Hi Tobias,
I was looking your input file, and I observed that you set
Max. gradient 0.00080
Try to set up the convergence criteria in a more consistent way.
For example: 
MAX_DR 0.001 
RMS DR 0.0003 
MAXFORCE 0.001 
RMS FORCE 0.0003

DR value set the spacing between the images of the atoms. Usually it is
sensitive to the roughness of the free energy landscape, thus, it
affects the efficiency of the TS search. In your case, changing the DR
value should not improve the result, anyway you can try to decrease it
(0.0005).

Luca

 
> Hello,
> 
> 
> I have tried out your suggestions regarding the dimer method, and in
> principle I have now successfully run this calculation. Unfortunately
> I didn't get the desired result, i.e. I didn't eliminate the spurious
> imagianary mode in the ts structure. What surprises me is the fact
> that there are hardly any noticable changes in the geometry. Changes
> affect the 3. and 4. decimal place of bond distances and angles
> (negliglible). What I expected to see are somewhat more noticable
> movements in those parts of the molecule which correspond to the small
> imaginary mode and should refine to a minimum (say small rotations of
> certain groups or other soft modes). This hasn't happened apparently,
> and hence the new structure is almost identical to the input
> structure, and hence - unsurprisingly - yields the same undesired
> imaginary modes again. I want to point out that this spurious mode is
> around 25 cm-1, a very soft mode, but it must be possible to get rid
> of it (and in fact, the constrained optimisation which I have used in
> another but related example did exaclty this). Could you advice me
> here in terms of parameters I should change. I have played around with
> the angle tolerance parameter, what about DR? Shoud I use tighter
> geometry convergence? At the moment I am more worried about the fatc
> that there is hardly any change in the geometry during the dimer
> optimisation. What protocols do you normally employ when you optimise
> to a saddle point of higher order? How do you refine the TS?
> 
> Thanks for your help (inputs plut other files attached)
> 
> Tobias
> 
>  
> 
> 
> 
>  
> 
> 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
>         
>         
>         
>         
>         &MOTION
>           &GEO_OPT
>             TYPE TRANSITION_STATE
>              &TRANSITION_STATE
>                METHOD DIMER
>                 &DIMER
>                 &ROT_OPT
>                   OPTIMIZER CG
>                 &END ROT_OPT
>                &END DIMER
>              &END TRANSITION_STATE
>             OPTIMIZER CG
>             MAX_FORCE 8.0E-4
>             MAX_ITER 500
>           &END GEO_OPT
>           &PRINT
>              &TRAJECTORY
>               &EACH
>                  GEO_OPT 1
>               &END EACH
>             &END TRAJECTORY
>           &END
>         &END MOTION
>         
>         
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