Application of the GCA to a series of curve crossing topologies

The generator coordinate approximation (GCA ) for the calculation of spectra of diatomics is briefly reviewed. Results of this method applied to a series of curve crossings are presented. In all cases, the generator coordinate method performs significantly better than does the adiabatic approximation. When the energy gap becomes smaller, the GCA results improve. In the crossing limit, the GCA becomes exact. © 1994 John Wiley & Sons, Inc.