COMPUTATIONAL DEVELOPMENTS IN GENERALIZED VALENCE-BOND CALCULATIONS

In this article a procedure for generating starting orbitals for gener alized valence bond (GVB) calculations is presented. This is achieved by selecting orbitals which correspond to specific bonds or electron p airs. These orbitals can be identified from the localized molecular or bitals, for both occupied and virtual orbitals, which are obtained thr ough a unitary transformation of the Hartree-Fock canonical molecular orbitals using the Boys's'localization method. A scheme has also been implemented which achieves optimum convergence of the pairwise orbital optimization. An object-oriented GVB program is developed which autom atically generates reliable initial GVB orbitals, leading to proper an d fast convergence. (C) 1996 by John Wiley & Sons, Inc.