output bond length with AIREBO potential?

Dear all,

I am wondering how to output the bond length information with AIREBO potential? I know that in AIREBO potential, the C-C interactions are not defined by bond_style,

Dear all,

I am wondering how to output the bond length information with AIREBO
potential? I know that in AIREBO potential, the C-C interactions are not
defined by bond_style, so there is no bond information associated with
neighboring carbon atoms. For a graphene sheet, I used AIREBO potential, how
can I get the C-C bond length? Thank you so much.

the easiest way to do this is probably in post-processing.
with VMD for example, you can select any pair of atoms
and then monitor the distance interactively or dump its
evolution to a file.

if you insist on dealing with this from inside of LAMMPS,
you could define bonds and then use bond_style none
(or harmonic with K=0 if that doesn't work). you only
have to make sure you set you special_bonds settings
to 1.0 1.0 1.0 so that no interactions are excluded.

axel.

Hi Axel,

Thank you so much. Appreciate! It helps a lot.

Best,

Justin

I wouldn't advise adding explicit dummy bonds.
If a pair of atoms moves far apart, which AIREBO
would allow, e.g. if you heat the system, then
the split bond will generate an error.

You could use dump local to output pairwise distances
from the neighbor list. If you restrict this to a group
that only contains C atoms, then you will get all the
C-C distances within some cutoff. I suppose a subset
of these are the C-C bond length you are looking for.
It depends on what AIREBO defines as a "bond",
since that is a fuzzy concept in a bond--order potential.

Steve

Hi Steve,

Thank you so much for the suggestion. My concern is that I need to find out the range of all c-c bond length. Some long bond length may be missed depends on the cutoff.

Best,

Justin

If the pair distance is longer than the neighbor cutoff (about 10 Angs
as I recall for AIREBO), then in what sense are the 2 atoms "bonded" ?

Steve