CNDO/CI calculations using symmetry orbitals

Typescript (photocopy).A new parameterization of the CNDO method is presented which correctly includes symmetry in the calculation. This new method is parameterized on the subshell level allowing each type of atomic orbital to be varied independently of the other orbitals. The point group of the molecule is determined by an analysis of the atomic coordinates and a set of projection operators is constructed. These operators are then used to find symmetry adapted linear combinations of atomic orbitals. The symmetry orbitals are then used to block factor the Fock matrix in the CNDO calculation. A configuration interaction calculation is also included which permits the use of multiply excited configurations. These configurations are then symmetry adapted and spin adapted before the final wavefunctions are calculated. Transition energies and oscillator strengths are found which are useful in the interpretation of experimentally obtained spectra. Preliminary results from these calculations for methane, benzene, and sulfur hexafluoride are discussed