[CP2K-user] NEB for diffusion energy barriers
Marcella Iannuzzi
marci... at gmail.com
Mon Dec 16 13:30:36 UTC 2019
Dear Stefano,
1) You can fix atoms, but this will not affect the computational time for
the NEB simulation.
2) The default for K_SPRING is good in most of the cases. I would keep it
unless you have a very good reason not to.
3) The NUMBER_OF_REPLICAS should be set such that the RMSD distance among
neighbouring beads does not exceed 1-2 Å
4) Be sure that you run on a total number of processors that is a multiple
of NUMBER_OF_REPLICAS*NPROC_REP
5) This should be easy to check by comparing the absolute values of the
coordinates.
Kind regards,
Marcella
On Monday, December 16, 2019 at 1:46:28 PM UTC+1, Stefano Ferrero wrote:
>
> Dear CP2K experts,
>
> I have just started using CP2K and I would be really thankful if anybody
> can help me.
> I am trying to calculate diffusion barriers of single atoms adsorbed on a
> surface using the NEB method.
> I optimized at DFT level the initial and final positions of the diffusion
> hop and I am providing those as first and last replicas.
> I have some questions about the set up of the calculation and the
> computational strategy to follow to obtain good results.
>
> 1) My system contains more than 200 atoms. Can I fix the atoms underneath
> the first layer of the surface to save computational time?
> 2) Should the value of K_SPRING be varied in order to see if there are
> changes in the results?
> 3) Should the value of NUMBER_OF_REPLICAS be varied in order to see if
> there are changes in the results?
> 4) Are there any other important parameters to take care of?
> 5) When plotting the energy profile of the NEB calculations I always find
> that the last frame, which I gave as an input, changes in energy with
> respect to the result found in the geometry optimization previously
> performed.Is it due to the ALIGN_FRAMES and ROTATE_FRAMES keywords, which I
> did not switched off?
>
> Is this a good strategy to obtain the diffusion energy barriers or would
> you suggest something else?
>
> I've attached the input file used and the geometries of the initial and
> final replicas.
> Thank you for your help!
>
> Stefano Ferrero
>
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