LAMMPS provides an overlay of different pair_styles using the "hybrid" keyword. If you apply a hybrid of "buck" and "zbl" for a similar set of particle types, the potentials are simply added together.

You should use a hybrid potential for combining these two potentials. Please study in details from here-

http://lammps.sandia.gov/doc/pair_hybrid.html

Mohsen Sadeghi & Jit Sarkar Does the hybrid overlay command combines the potentials by interpolation??? I want to combine it using spline interpolation.

@Qiagshun Guan

Yes my problem is solved. I used atsim.potentials package with lammps. See this link. https://atsimpotentials.readthedocs.io/en/latest/potentials/pair_potential_tabulation.html#example-spline

The method is exactly the same as you have described as tabular method. It does exactly the same by generating a file that stores data for spline interpolation.

Hi Afza, as a quick follow up to this, were you using the Teter parameters for the buck potential? I followed the atsim tutorial and it was great, but I want to make sure I am implementing it properly in LAMMPS. If we are working on similar problems I would be happy to share my finished potential.

Also, as a specific question, when implementing the table in lammps did you use pair_style table linear or spline

Did you keep the 6500 entries?

Thanks!