[CP2K-user] NEB for diffusion energy barriers

Stefano Ferrero stefano.... at edu.unito.it
Thu Dec 19 10:10:47 UTC 2019

Dear Marcella,

Thank you very much for your help

Kind regards,

Il giorno lunedì 16 dicembre 2019 14:30:36 UTC+1, Marcella Iannuzzi ha 
> 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 
> 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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