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The springs should distribute the images evenly along the NEB path during the optimisation, and the choice of $ k_{spr}$ must be made at the beginning of each run. It has been suggested by Jónsson and coworkers that since the action of the springs is only felt along the path the value of the spring constant is not critical as long as it is not zero [27]. If $ k_{spr}$ is set to zero then sensible behaviour occurs for the first several tens of iterations only; even though $ \gtpar $ is projected out, $ \bft $ fluctuates and further optimisation will eventually result in the majority of images gradually sliding down to local minima [27].


Semen A Trygubenko 2006-04-10