Optimization of basis sets in valence bond calculations

Using the symmetry of the molecular point group, the Hamiltonian matrix is factorized. At the same time, the chemically inequivalent configurations ar e used to calculate the entries of the Hamiltonian matrix directly. This me thodology saves a large amount of computer memory and computational time, e specially for pi-systems with more than 20 pi-electrons. (C) 1999 Elsevier Science B.V. All rights reserved.