Potential fitting for radiation damage

I was going through the following paper on radiation damage " Gray, R., Rushton, M. J., & Murphy, S. T. (2022). Molecular dynamics simulations of radiation damage in YBa2Cu3O7. Superconductor Science and Technology ." in order to understand the potential development and fitting procedure. I was able to understand up to the splining of Buck and ZBL potential using ATSIM package but could not get the methodology used for potential fitting in section 3.2. So what is the need of potential fitting after splining the above mentioned potentials?

Sorry, but you are asking off-topic questions here. This nothing to do with LAMMPS outside of you using LAMMPS. LAMMPS does not care how and why you create your potential file for as long as they are in the correct format.

I apologize. I wondered if I can find any lead here.

If you want to discuss details of a paper, you should discuss it with the authors.