I assume that you want to model how the oxygen atom migrates or diffuses in the interstitial region of Ni-based metal. With the LAMMPS package, you are trying to solve this problem with classical molecular dynamics. How to interatomic potentials is important but kind of tricky. However, you can use the Nudged Elastic Band (NEB) method to find the migration path from the angle of the fist-principles.
The nudged elastic band (NEB) is a method for finding saddle points and minimum energy paths between known reactants and products. The method works by optimizing a number of intermediate images along the reaction path. Each image finds the lowest energy possible while maintaining equal spacing to neighboring images. This constrained optimization is done by adding spring forces along with the band between images and by projecting out the component of the force due to the potential perpendicular to the band.
In detail, you can use this method in the VASP package with the VTST function.