Equivalence of the Sun and Tietz potential models for diatomic molecules

We show that the Sun potential energy model is equivalent to the Tietz potential energy model for diatomic molecules. We evaluate the accuracy of the Tietz potential model in reproducing the interaction potential energy curve of the A1 ∑ u + state of Na2 molecule. The average absolute deviation of the Tietz potential for the A1 ∑ u + state of Na2 from the experimental RKR potential satisfies the Lippincott criterion.