ReaxFF: bond order and bond breaking

Hi all,

by default LAMMPS takes 0.3 as the bond order at which the bond “breaks” or “emerges”. What are the considerations that explain this value? Maybe there are any related studies/papers? More generally, are there reasonable means to estimate that “threshold” bond order for a given pair of elements?

I’d appreciate if Ray or Aidan could comment.

Regards,
Oleg.

Oleg,

The "0.3" is just an example value and should be used with discretion.
Chenoweth et al in their 2008 CHO paper used a universal value of
0.2, while Budzien et al (co-authored with Aidan) in the 2009 JPCB
paper used a much more complicated combination of cutoff values (Table
1).

A single bond has a BO of 1.0 and a double bond 2.0. Longer the bond
length is, weaker the bond order. So you can interpret a bond order
cutoff of 0.3 being an extended distance cutoff for determining bonds.
Method described by Goldman and Tamblyn in their 2013 paper outlined
a distance-based criterion for determining bonds. I would imagine
something similar can be done for bond order-based criterion.

Cheers,
Ray

Ray,

thanks for the answer, I think it may be interesting to compare the approaches. And in your paper with Wixom, Mattsson and Thompson (J. Phys. Chem. B, 2013, 117 (3), pp 928–936) you say that you use the same parametrization that Budzien et al. - does it also mean that you used the same threshold bond orders?

Regards,
Oleg.

05.09.2013, 19:38, "Ray Shan" <[email protected]>:

Oleg,

Yes, same set of cutoffs were used in that study, but I do use
different cutoff values for different materials.

Cheers,
Ray

Of course. Thanks again for clarifications.

Regards,
Oleg.

06.09.2013, 03:19, "Ray Shan" <[email protected]>: