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I am relatively new to electronic structure calculations, and I am trying to figure out the most appropriate way of scanning a potential energy surface (PES) to locate an appropriate transition state.

The proposed reactants and products can be found at the bottom of this post (only the relevant fragments are shown).

What is the most appropriate PES scan to perform? It seems logical to scan through possible values of the bond length between atoms 9 (blue) and 6 (red). But should I actually be doing a two-dimensional scan, the other dimension being the bond length between atoms 9 (blue) and 4 (orange)? Or perhaps the bond angle between atoms 9-6-5 is better? I read that doing a two-dimensional scan over two parameters that are related to the same structural parameter may not be ideal.

Any suggestions would be greatly appreciated!

Reactant:

Reactant

Product: Note that N2 is also the product but is infinitely separated.

Product

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    $\begingroup$ Why not search for the TS first and then decide what the best coordinates are (most likely the bonds broken/build up)? $\endgroup$
    – DSVA
    Mar 13, 2017 at 20:10
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    $\begingroup$ Hi @DSVA. Yes, that is what I ended up doing. It seems that the 1-D scan of the bond length between atoms 6 and 9 produced a maximum that was close to the transition state, which I then found and confirmed via an IRC calculation. I suppose it was best to search first then decide, as you suggested. I just wasn't sure if there was a general rule of thumb or flow of logic that I was missing. $\endgroup$
    – Argon
    Mar 14, 2017 at 1:40

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