Comparison of CI-NEB and Dimer Methods for Transition State Localization

[nidhit]

I'm curious about the effectiveness of two methods, CI-NEB and Dimer, in finding transition states. (i) Which one of the two is better? (ii) What criteria can be used to determine the accuracy of the transition state obtained through CI-NEB?

[nidhit]

In a follow up to the above question, what should we do when we get two imaginary frequencies in the transition state obtained using CI-NEB? For example, I looked into the CO+O -> CO2 step on 3X3 Pt(111) with sufficient vacuum slab. The initial and final states are optimized and the CI-NEB calculation is converged but the frequency analysis gave two imaginary values of about 340 cm-1 and 150 cm-1. Should I consider my transition state to incorrect? What should be done if that is the case? I have attached the files of both CI-NEB and Frequency calculations in the .zip format. Please check and shed some light on this issue.