Tabulated potentials are defined as a table of potential function values at discrete sampling points. potfit will interpolate between the sampling points to get potential values for all required interatomic distances.

While this may require more paremeters than the analytic variant it also allows for much greater flexibility in the potential function itself. While an analytic potential is bound to the parametric function and the resulting set of possible potential function, a tabulated potential can assume (almost) any discrete value at each sampling point.

A disadvantage of this type of potentials is the locality of the individual potential values. To provide a meaningful and transferable potential potfit requires reference data at all distances. If there is no reference data available for a certain distance, the potential value at this sampling point may assume a wide range of values without changing the target function at all. Such behavior is problematic for many optimization algorithms and needs to be watched closely while fitting a potential. Using the bindist option can be useful to check the distribution of available reference data with respect to the sampling points.