I am currently trying to use the dimer routines in TSASE to calculate some reaction barriers with GPAW. However, I run into a small problem wherein I can reach the force convergence, but the curvature is positive. Thus, what I end up with is something that looks like:
4 0.139406 1.507605 443.900317 16
alpha=vmag(Fperp)/vmag(F0): 0.946011
curvature: 1.396486
drag up directly
Ftrans 0.110369451764
5 0.046732 1.396486 443.898168 20
alpha=vmag(Fperp)/vmag(F0): 0.991729
curvature: 0.548309
drag up directly
Ftrans 0.0455703394463
6 0.021699 0.548309 443.896273 24
alpha=vmag(Fperp)/vmag(F0): 0.988442
curvature: 10.372543
Ftrans 0.353999654585
7 0.154144 10.372543 443.901679 28
I am using the internal search function that is included with the ssdimer class.
As anyone else seen a similar behavior?
GPAW with TSASE
Moderator: moderators
Re: GPAW with TSASE
The dimer wouldn't stop if the curvature is positive. In your post, the last step (step 7) has a negative curvature. You can set a tighter convergence criteria, for example 0.03, to let the dimer run more steps.
For the first few steps the curvature is positive and the force is small, which indicates the initial guess is very close to a minimum.
For the first few steps the curvature is positive and the force is small, which indicates the initial guess is very close to a minimum.

 Posts: 2
 Joined: Fri Apr 03, 2015 3:38 pm
Re: GPAW with TSASE
A tighter convergence criteria won't help. It's already at 0.05 eV/Ang, and while it'll dip below 0.05, the curvature won't be negative, and thus it keeps cycling through.
Re: GPAW with TSASE
In that case, you may want to push the initial guess a little further from the reactant minimum. It is better to start outside the concave region to get rid of those concerted mode.
In sum, try a better initial guess. At the same time, set a tighter rotation convergence: rotationMax = 20, phi_tol=3
In sum, try a better initial guess. At the same time, set a tighter rotation convergence: rotationMax = 20, phi_tol=3