Adding a repulsive correction at short distances to Buckingham potential

LAMMPS LAMMPS General Discussion
1

I am using a Buckingham potential (BP) for my simulation involving high temperature melting. When I simulate at low temperatures, there is no issue with the simulation. But when I start moving to higher temperatures to create a melt, I get lost atoms probably because the forces are too high due to the unusual behavior of BP at low separation between atoms. I have seen people using spline correction with other codes like DL_POLY. Is there a similar fix to this problem?

Thank you in advance.

2

You have two main options that do not require changing the LAMMPS source code:

  • create customized tabulated potentials. You can use the “pair_write” command to write out the current potentials as reference and then augment the part that you want to make more repulsive.
  • use pair style hybrid/overlay with a repulsive-only potential (e.g. lj/cut or morse with the cutoff set to the minimum and shifted so its energy is 0 at the cutoff). This way you can add a repulsive contribution to the buck pair style
3

Thank you so much akohlmey.
The first solution you suggested will involve writing down the potentials (energy/forces as a function of distance) in a file, modifying the low-r values to make them repulsive, and then using the modified file as inputs to the simulation. Is that right?

4

Hi, I have the same problem here. Any examples for method 1? Cause it seems more direct to me.

5

There is now a python module that can help to build the tables. 10. Auxiliary tools — LAMMPS documentation

6

Thank you for your reply.