I have read G. Henkelman's two papers on CNEB publised in 2000, and several posts in this forum. I am still confusing on what the forces convergent criterion standing for.
In the screen output when running the nebef.pl,
The second column sem to be the forces from /grep "max atom" OUTCAR/.
But, in my opinion, the forces shoud be the spring force parallel to th the tangent and the real force perpendicular to the tangent, or the sum of the two parts, which is added to the image, rather than any single atom.
Can any body give me some advice?
What does the EDIFFG stand for for a CNEB run?
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cenwanglai
- Posts: 46
- Joined: Sun Jun 13, 2010 5:46 am
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cenwanglai
- Posts: 46
- Joined: Sun Jun 13, 2010 5:46 am
Re: What does the EDIFFG stand for for a CNEB run?
In this thread viewtopic.php?f=2&t=837
Graeme said the second column for nebef.pl output is the forces projected along the reaction pathway. But, as mentioned above, it is right exactly? I have checked the nebef.pl script and found that the second column is the forces according to grep "FORCES: max atom" OUTCAT.
Graeme said the second column for nebef.pl output is the forces projected along the reaction pathway. But, as mentioned above, it is right exactly? I have checked the nebef.pl script and found that the second column is the forces according to grep "FORCES: max atom" OUTCAT.
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cenwanglai
- Posts: 46
- Joined: Sun Jun 13, 2010 5:46 am
Re: What does the EDIFFG stand for for a CNEB run?
I have check the code nebbarrier.pl, where I can find the $force='grep "NEB: projections" $directories[$i]/OUTCAR | tail -1', and then
@force=split(/\s+/,$force);
$force=$force[@force-1];
In one of my OUTCAR, the line "NEB: projections" read like : NEB: projections on to tangent (spring, REAL) -0.425069 0.137351
So, the last $force=0.137351.
As results, the nebef.pl and nebbarrier.pl provide different forces. The former corresponds to "FORCES: max atom", and the latter to REAL force projected to the tangent of the reacton path, excluding the spring forces.
I am confused! And, I do not know what kind of forces, or what components of forces push the images and atoms in the images down to the MEP.
@force=split(/\s+/,$force);
$force=$force[@force-1];
In one of my OUTCAR, the line "NEB: projections" read like : NEB: projections on to tangent (spring, REAL) -0.425069 0.137351
So, the last $force=0.137351.
As results, the nebef.pl and nebbarrier.pl provide different forces. The former corresponds to "FORCES: max atom", and the latter to REAL force projected to the tangent of the reacton path, excluding the spring forces.
I am confused! And, I do not know what kind of forces, or what components of forces push the images and atoms in the images down to the MEP.
Re: What does the EDIFFG stand for for a CNEB run?
The nebef.pl script gives tells you about the NEB force on each image. This is the sum of the real force perpendicular to the band and the spring force parallel to the band. These are the forces that should drop below your convergence criteria.
The nebbarrier.pl script uses the real force along the band to interpolate the energy between the images and give you a plot of the energy barrier. These forces give the slope of the energy vs reaction coordinate; they do not go to zero for a converged band.
The nebbarrier.pl script uses the real force along the band to interpolate the energy between the images and give you a plot of the energy barrier. These forces give the slope of the energy vs reaction coordinate; they do not go to zero for a converged band.