Bond order cutoff


Anyone please clarify what is bond order cutoff? What’s the difference between bond lengths between an atom pair and their corresponding bond order cutoff?


Please provide some context.

Length and bond order are two very different properties.

Dear Akohlmey,

Thanks for your response. Actually, I am trying to calculate species evolution (particularly Li2O2) during MD simulation using " reax/c/species" fix. Reax/c/species requires bond order cutoff for Li-O and O-O atom pairs to successfully represent Li2O2 formation. Though default bond order value is 0.3 for all type of atom pairs, however, this is not the case for Li2O2 formation. I have bond lengths for Li-O (1.91 angstrom) and Li-O (1.58 angstrom) in Li2O2 molecule but don’t know exact bond order cutoff for these atom pairs.

That’s what I am trying to ask what is bond order cut off and how to calculate for the aformentioned atomic pairs?

Khizar Hayat

Bond order is a concept from chemistry and thus you probably are best off digging out a corresponding text book. It also is a property that is computed during the calculation of the ReaxFF potential and a measure for the “order” of a bond. So you should also read up on the ReaxFF publications. The bond order cutoff in fix reaxff/species then is an empirical value determining when an interaction between two atoms is strong enough to be considered a bond. I cannot tell you what is a suitable cutoff value for your specific compound. That requires specific knowledge of the chemistry of your reactions.

P.S.: if you want to do a more complex and specific bond analysis, you may instead consider using fix reaxff/bonds and only dump the “raw” bond information data as accumulated internally by the ReaxFF potential and then write your own analysis software to post-process that data.

Sure. Thank you.