How does FMAGFLAG effect a ClNEB run?

[cenwanglai]

How does the FMAGFLAG changes the convergent forces criterion?

It is really necessary to set FMAGFLAG tag in INCAR for a ClNEB run?

How to set this tag? FMAGFLAG = .TRUE.?

[cenwanglai]

For a standard vtstcode included vasp, the forces in the OUTCAR may be read like below:

NEB: the previous image is higher in energy: F
NEB: the next image is higher in energy : F
NEB: image is at an extrema
NEB: diff energy (min, max): 762.479528 762.479528
NEB: forces: par spring, perp REAL, dneb 304.963231 0.478778 0.000000
NEB: distance to prev, next image, angle between 69.443272 8.450626 91.535402
NEB: projections on to tangent (spring, REAL) -304.963231 -0.322032

FORCES: max atom, RMS 0.184192 0.052673
FORCE total and by dimension 0.577003 0.171505

For a ClNEB run without FMAGFLAG set in INCAR, the nebef.pl searchs for "FORCES: max atom" and the value 0.184192 to compare with the force criterion EDIFFG(< 0).

If FMAGFLAG set in INCAR, which kind of forces will be chosen to compare with the convergent force criterion?

[graeme]

When the FMAGFLAG is set, the the convergence criterion is based upon the total RMS force for all atoms instead of the max RMS force for any atom.