Configuration interaction calculations for the N 2 molecule and its three lowest dissociation limits
A series of multi-reference double-excitation CI calculations is reported for the N 2 molecule in its equilibrium conformation as well as for its three lowest dissociation limits 4S + 4S, 4S + 2D and 4S + 2P respectively. Special emphasis is placed upon satisfying the requirement that the molecular CI energies at large internuclear separations must converge to the same values as are obtained in an analogous treatment for the corresponding atomic limits. In the most extensive CI undertaken the lowest three dissociation limits are calculated to occur at 9.33, 12.08 and 13.39 eV respectively compared to the experimental values of 9.90, 12.29 and 13.48 eV. The advantages of employing bond-centered functions in obtaining the proper balance between the bound molecule and its dissociated atoms are underscored in the calculations.