[CP2K-user] [CP2K:18254] TS Dimer method gives unphysical results

DMT dobromirak at gmail.com
Sun Dec 25 23:14:34 UTC 2022


I tried to use the Dimer method of optimizing TS and I get unphysical 

I used this google group to find different input files and read about the 
struggles to overcome and used the provided input settings of successful 

In both cases (files attached include input, required .xyz and output .xyz 
from the optimization) Dimer drives the structures into having impossibly 
short bonds, until the SCF does not even want to converge (and it would be 
obviously impossible). It literally tries to merge some atoms in both 
cases. I use the &DIMER_VECTOR to input the XYZ displacements from a 
VIBRATIONAL_ANALYSIS job for the Reaction Coordinate that I am interested 
in, using the guessed near-TS geometries. Without the DIMER_VECTOR the 
method always chooses a wrong Reaction path. In both cases the TS geometry 
I start with is very simple to provide, in fact I have found both TS with 
other software, it is just very important for me to try simple systems in 
cp2k before I move to actual research.

One of the reactions is substitution in which the N LP from NH3 attacks the 
C of CH3Cl and pushes the Cl away to form a quaternary ammonium cation with 
the Cl- around. The other reaction is monomolecular - a keto-O taking a H 
from a nearby amino group into an alcohol-imin as a Product.

I have already tried higher values for EPS_DEFAULT (1.0E-13) and EPS_SCF 
(1.0E-7), and nothing changes.

I feel like the Dimer simply doesn't know where to stop with increasing the 
Energy. Perhaps the choice of DFT (PBE) and basis (DZVP-MOLOPT-GTH (a good 
basis)) is bad for the particular PES ?

I would like any advises at all. Do you have success using the Dimer method 
? Can you provide input files from successful runs, other than the ones 
already in the group conversations ?

Best Regards,

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