Pair_style for system composed of N and C

LAMMPS LAMMPS Beginners
1

Dear experts
Sorry for my beginner question, I would like to use a forcefield for a system composed of N and C to deal with coupling and divergence between C-C, N-N, and N-C. I’m currently using the following configuration of the forcefields.

pair_style hybrid/overlay airebo 3.0 tersoff
pair_coeff * * tersoff BNC.tersoff C N
pair_coeff * * airebo CH.airebo C NULL

, but please let us know if there is a more appropriate/useful forcefield file or configuration.

2

Yours is a very bad choice. You are treating many-body potentials as if they are pair-wise additive, but they are not. This has been discussed a lot in the past, so search the forum archive for previous discussions.

There are two basic rules you should remember:

  • do not use a hybrid pair style to “mix” many-body potentials if you can avoid it. If you must use pair style hybrid, the cross-terms must be provided by a pairwise additive potential like lj/cut or morse
  • when using multiple many-body potentials in a hybrid potential, make sure they do not share an element assignment.
3

Dear akohlmey
Thank you for the comment,

I cheked this page for hybrid style pair_style hybrid command — LAMMPS documentation and
lammps-tersoff-vector/machines/lammps-10Mar16/doc/pair_hybrid.txt at master · HPAC/lammps-tersoff-vector · GitHub

Would you teach me some examples to handle the N, C system?
Just below is much proper to handle the N, C system?
pair_style tersoff
pair_coeff * * BNC.tersoff N C

Best regards

4

Do you seriously think that a hacked version of LAMMPS from 8 1/2 years ago from some random person on GitHub is a credible source compared to that actual up-to-date online version of the LAMMPS manual prepared and maintained by the real LAMMPS developers?

That is the job of your adviser or tutor and not myself (I have already enough people that I am teaching stuff) or the forum (this is to discuss LAMMPS issues not how to set up simulations).
I have already given you the basic gist of how you have to approach this, yet you to seem to prefer ignoring it and are unwilling to draw your own conclusions. On that basis, I have to interest to continue this discussion. You’ll have to wait for somebody else to want to chime in or need to consult the people that are actually in charge of (and get paid for) training you.