The potential formats 3 and 4 are used for tabulated potentials. Format 4 allows arbitrary sampling points for the potential function tables and supports all header lines.

As with potential files in format 3 each data column has its own spacing. But with potential format 4 the requirement that the sampling points be equidistant is dropped. Arbitrarily spaced sampling points are possible, but the sampling points have to be given in order.

Preceding the data columns is a header with one line per column, containing the number of sampling points in the corresponding column. Seperated by blank lines then the data columns follow. Each of the columns has the form

r_0     f(r_0)
r_1     f(r_1)
...
r_steps f(r_steps)

Please note that $r_0 < r_1 < \ldots < r_{steps}$ is required. The order of the columns is the same as with format 3.

Similarly as for format 3, for potential functions that are a function of distance (e.g. pair potentials, EAM transfer functions), a smooth cutoff at the final sampling value is assumed and the value is not varied.

A sample format 4 potential file for a binary system (EAM potential) is available here (with the #G header line).