[Pw_forum] NEB: Huge error for first image

[Maxim Skripnik]

Dear developers,

I perform NEB calculations with an electric field (eamp != 0). The first 
and last images are relaxed with pw.x with a specific value for eamp. 
The relaxed xyz coordinates are then used for the neb calculation. 
However, the error for the first image is really high (above 25 eV/A). 
In some cases it even doesn't fit in the reserved decimal places (see 
below). Is this an issue which has to be dealt with or can one neglect 
this? I don't understand why the error is so big while the structure has 
been properly relaxed.

The NEB calculation converges to reasonable activation energies, even 
though the error of the first images stays at a high value. I just want 
to ensure that this is not an issue. Maybe one of the developers can 
explain why the error is so big?

Best regrads
Maxim Skripnik
Univ. Konstanz

      ------------------------------ iteration   2 
------------------------------

      tcpu =   3835.6    self-consistency for image   2

    Info: using nr1, nr2, nr3 values from input

    Info: using nr1, nr2, nr3 values from input
      tcpu =   4152.5    self-consistency for image   3

    Info: using nr1, nr2, nr3 values from input

    Info: using nr1, nr2, nr3 values from input
      tcpu =   4510.8    self-consistency for image   4

    Info: using nr1, nr2, nr3 values from input

    Info: using nr1, nr2, nr3 values from input
      tcpu =   4856.1    self-consistency for image   5

    Info: using nr1, nr2, nr3 values from input

    Info: using nr1, nr2, nr3 values from input
      tcpu =   5176.3    self-consistency for image   6

    Info: using nr1, nr2, nr3 values from input

    Info: using nr1, nr2, nr3 values from input

      activation energy (->) =   0.776966 eV
      activation energy (<-) =   0.435476 eV

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

          1     -27262.4585336          **********            T
          2     -27262.3382765            2.780244            F
          3     -27262.1422089            1.372929            F
          4     -27261.8032661            1.653251            F
          5     -27261.6815672            1.336730            F
          6     -27261.9419108            0.967285            F
          7     -27262.1170431            0.002386            T

      path length          =  4.553 bohr
      inter-image distance =  0.759 bohr