A FORMULATION OF MULTIPLE-REFERENCE CT WITH TERMS LINEAR IN THE INTERELECTRONIC DISTANCES .2. AN ALTERNATIVE ANSATZ

An alternative ansatz for r(12)-MR-CI is given. The final formulas are much more easily obtained than was possible previously. The numerical performance is demonstrated with a model calculation of the ground st ate of helium using three different Gaussian basis sets (5s, 10s, 16s) . With the two largest basis sets, the energies obtained with the new formulas, the formulas of Part I of this series of articles, and the f ormulas of the original formulation agree within 2 mu E(H). Since the new ansatz is much easier to handle mathematically, we recommend its,u sage for future work. (C) 1995 John Wiley and Sons, Inc.