Dear all,
When using the built-in NEB method in VASP, I noticed that increasing the number of intermediate images does not necessarily result in a finer resolution of the transition path.
In a typical example, I performed NEB calculations on the same initial and final states with two different settings: IMAGES=7 (Figure a) and IMAGES=18 (Figure b). The energy profiles are plotted below:
(Public link if figure not shown)https://imgur.com/a/4tihxkF
In both Figures a and b, each point corresponds to one image. The horizontal spacing between neighboring points represents the root sum squared distance between configuration files, calculated using the VTST script nebresults.pl.
Surprisingly, the result from IMAGES=18 does not appear more refined than that from IMAGES=7. This is because many of the added images do not reflect any significant structural transition. In fact, images 0–7 and 12–19 (Figure c) correspond mostly to trivial translations. The actual transformation occurs only within a narrow range (images 7–12), which is not much improved compared to the IMAGES=7 case.
This issue resembles a well-known problem in traditional elastic band algorithms, where intermediate images tend to slide toward the endpoints. In my case, this still happens despite the increased number of images.
My question is: Is there a way to get a more uniform distribution of the intermediate images along the actual transformation path and see more on the transition path? Otherwise, simply increasing the number of images becomes ineffective.
Thanks!
