[Pw_forum] zero activation energy in NEB calculations

[Giuseppe Mattioli]

Dear Manjusha

      activation energy (->) =   0.000000 eV
      activation energy (<-) =   0.000000 eV

      image        energy (eV)        error (eV/A)        frozen

          1     -64917.3691663            3.118784            T
          2     -64919.6863336            2.357326            F
          3     -64918.3306026            3.752568            F
          4     -64918.3307659            3.754808            F
          5     -64919.6865281            2.355640            F
          6     -64917.3691661            3.119165            T

      path length          =  7.684 bohr
      inter-image distance =  1.537 bohr

It seems that your first and last images are not potential energy  
minima. Try to optimize their geometry and check if, after  
optimization, they are still what you expect. Then perform the neb  
calculation.
HTH
Giueppe

Giuseppe Mattioli
ISM-CNR
Italy

Quoting manchugh at iitk.ac.in:

> Dear all
>
> I am doing NEB calculation to find the MEP between two states using
> version neb-5.0.2. First, I want to get the path trajectory using no-CI
> and after 10-15 iterations, if the path trajectory is stabilized, I will
> use CI. But after 2nd iteration in my no-CI calculation, I am getting zero
> activation energy. My system is Ga terminated surface of GaN(0001) and one
> N atom is diffusing from one fcc site to another for which I am
> calculating MEP.
> Input and output files are attached. (The output is not complete since job
> is still running). Can anyone clarify why activation energy is zero?
>
> Thank you for your time
> Manjusha
> IIT Kanpur
> India


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