Does it make sense to set SPRING= -4 or -3 ?

[ross]

Hi, everyone:
Recently when performing the NEB, I encounted the convergence problem. Forces in one IMAGE are as follows
FORCES: max atom, RMS 0.063526 0.036842
FORCES: max atom, RMS 0.063462 0.036976
FORCES: max atom, RMS 0.064805 0.037374
FORCES: max atom, RMS 0.066617 0.037910
FORCES: max atom, RMS 0.068232 0.038739
FORCES: max atom, RMS 0.070051 0.039877
FORCES: max atom, RMS 0.072115 0.041121
FORCES: max atom, RMS 0.074126 0.042747
FORCES: max atom, RMS 0.079863 0.044386
FORCES: max atom, RMS 0.085447 0.046197
FORCES: max atom, RMS 0.091900 0.047981
FORCES: max atom, RMS 0.097571 0.049915
FORCES: max atom, RMS 0.102573 0.051779
FORCES: max atom, RMS 0.107014 0.053679
FORCES: max atom, RMS 0.110360 0.055417
FORCES: max atom, RMS 0.114551 0.057225
FORCES: max atom, RMS 0.120333 0.058827
FORCES: max atom, RMS 0.122836 0.060597
FORCES: max atom, RMS 0.123830 0.062236
FORCES: max atom, RMS 0.123374 0.063605
FORCES: max atom, RMS 0.122386 0.064960
FORCES: max atom, RMS 0.122792 0.066034
FORCES: max atom, RMS 0.129444 0.066882
FORCES: max atom, RMS 0.134568 0.067313

At the same time other IMAGES' FORCES do not decreased. I have tried to change the IOPT, however, it did not work well.
My questions is if I just want to get the migration energy,i.e. the position and energy of the saddle point, can I use the smaller spring force(SPRING=-4 or -3) to increase the convergence withou affecting the saddle point since as far as I know no spring force applied on the saddle point ?
Another question is that what is the reasonable convergence criterion when running the NEB. IS 0.08 ev/A ok?
Best wishes

[graeme]

The spring force will have almost no effect on the calculation; you can safely leave it at the default.

A force criteria is 0.08 is probably ok, but going to 0.01 would be safer.