[lammps-users] Carbon nanotube


I am trying to replace one Hydrogen in the structure of CNT with an AIREBO potential function. When I use “fix nvt” and I see the output, I see that the Hydrogen atom (or even atoms) do not have any displacement and all also the velocity components are zero.
The same thing happend for Si while using TERSOFF potential function.
Would anybody tell me please, if I am doing something wrong? It seems strange that these atome are completely fixed in their positions.

Best regards

Dear Mehrdad.

  1. Are you using setforce command on those atoms?
  2. If not, the displacement and velocity component equal to zero mean that there is no force acting on those atoms. Have you included them into the interaction potential
  3. The tersoff potential is a short range potential with a cutoff of around 2 Angs. So, if the atoms are separated by more that this distance, they wont feel each other. Is that your case.
  4. Have you included those atoms into the integrator (nvt, or others).

For every problem there is a solution. You have to tackle it step by step and see what may be going wrong. Best of luck. I hope this may help you figuring out what may be going wrong.

Dear all,

In relation to modeling CNT, I have a question. When we use AIREBO/Tersoff potentials, we are essentially describing how atomic interactions are occurring. Do they implicitly consider the bond interactions between atomic pairs, or should another command like bond_style be invoked to initiate such bond interactions? If yes, then apart from atomic coordinates, bonds in the CNT will also be important when defining the geometry of the system. Please suggest.


bond interactions are implicit (as these are bond order potentials). You dont need to define them explicitly in the files.