Peculiarity of the Dickinson H 2 + wave function

According to the zero potential energy criterion proposed recently, the Dickinson wave function for the 2p_u state of the H₂⁺system is an unexpectedly poor approximation so long as the known parameters are employed. We re-examine the optimum parameters for the Dickinson wave function and find that there exist two sets of optimum parameters with different wave function characteristics. The corresponding energy curves cross at R= 1.91 a.u., though the difference is very small. We suggest that a new set of optimum parameters with slightly higher energy for R>1.91 a.u. is more acceptable physically than the previously reported set.