A new potential function form incorporating extended long-range behaviour:: application to ground-state Ca2

A new analytic potential energy function form which incorporates the two leading inverse-power terms in the long-range potential is introduced and applied to a recently reported data set for the ground X-1 Sigma(+) state of Ca-2. The new function yields an accurate representation of data which span 99.97% of the well depth and involves only a fraction as many (between 1/3 and 2/3 fewer) parameters as were needed to define published potential functions for these systems based on the same data. Fits using this form also allow a robust determination of the dissociation energy and C-6 dispersion coefficient, and the resulting function is easier to use than other potential functions which have been determined for this system.