The cutoff distance r_max is the smallest positive value for which du(r)/dr=0 and is obtained by iterative solution of the above equation. The reason a cutoff distance is required is that at very short distances, the original Buckingham exponential-6 potential becomes negative.

The radial distance for which u(r)=0 can also be computed from the potential. It is denoted by s and is used to normalize the thermodynamic properties, for consistency with the commonly used Lennard-Jones potential.

Cross interactions are computed as follows: