Interpolated sets allows to represent atomic movements between an initial and final positions, and thus can represent chemical reactions. The initial and final positions must therefore contain the same atoms, with only positional changes.
Multiple intermediate (or "interpolated") structures, referred to as images, of the system being considered need to be generated by interpolation in between these initial and final configurations, by varying linearly the one-dimensional reaction "coordinate" (e.g. the atomic positions) from its initial to final value.
This set of initial and final structures together with images ordered in a particular manner constitutes the interpolated set for the chemical reaction.
Interpolated Sets are used for the calculation of the energy profile and activation barrier for the chemical reactions via the Nudged Elastic Bands (NEB) method.
In the animation below, we generate an interpolated set with 5 intermediate images from a pair of initial and final structures.